The obvious WWII alternate history question is how could the Axis have won. Let's try something different this time.

The Battle of France was a big gamble for the Third Reich. They sent more or less their entire army in a rush attack in order to secure a fast victory. You may be reminded of the Schlieffen Plan in WWI. It worked this time, but had it not, they would have been in a dire situation.

Had their army been destroyed, there would not have been enough left to defend German territory. Had they been forced into a more static war of attrition, France and Britain would have had time to reorganise their military, with the support of their respective colonial empires and access to American industry - and the Axis may have not been in a better position to fight a new WWI than the Central Powers had been.

So be it with a swift counter-attack or a slow, bloody grind, what is the smallest change that could have resulted in an eventual Allied victory in the Battle of France?

The customary disclaimers apply:

  • It doesn't have to result in a global Allied victory with the fall of Berlin and Rome, but it has to significantly increase its probability.
  • A victory doesn't mean the entire Axis is defeated, only the European part. Japan can be victorious in the Pacific Ocean at the same time, for example.
  • The change has to be a single event, or a collection of tightly coupled and interdependent events, ideally the starting point an otherwise trivial change. It has to happen either during the war, or not more than a few years before it. The war should, at least in the beginning, look very similar to what happened in real life: the alliances should be roughly the same, the events like the Anschluss, the conquest of Poland, the attack against France and the Low Countries should occur (or at least begin), even if at different dates or different order. The major participants should be the same.
  • The change should have a realistic justification (so no secret Belgian superlaser), no unrealistic decision like continuing the very expensive Maginot Line until the sea without a very solid reason, no sudden change of doctrine just because some general had an epiphany about revolutionary new tactics...
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    $\begingroup$ What an interesting question! I just finished reading Dwight Eisenhower: Supreme Commander, which left me with the question about how in the world France was defeated so quickly. I'm looking forward to the answers and hopefully a reference for a book or two to give insight. $\endgroup$ Commented Feb 1, 2018 at 22:08
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    $\begingroup$ I wonder how literal the question is. The Allies could have avoided the Battle of France altogether by attacking Germany while the Germans were busy invading Poland, and probably win the war. Would that count as "winning" the Battle of France? $\endgroup$
    – Semaphore
    Commented Feb 2, 2018 at 13:22
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    $\begingroup$ @Semaphore It would essentially be the same battle happening differently, similarly to a battle happening only on the territory of Low Countries. So while it would be remembered under a different name, it would qualify. The question is, of course, what event could have caused such a major doctrinal change (and not have it backfire with a half-backed attack ending in disaster for other reasons). $\endgroup$
    – Eth
    Commented Feb 2, 2018 at 16:36
  • $\begingroup$ well, now I want to play Axis & Allies. : ] $\endgroup$
    – tex
    Commented Feb 2, 2018 at 22:15
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    $\begingroup$ Sounds like a question a time traveler would ask. $\endgroup$ Commented Feb 5, 2018 at 7:55

22 Answers 22


The French listen to Belgian intelligence.

The Belgians had surprisingly good intelligence about what the Germans were planning. They'd identified the German military buildup, and considered an invasion through the Ardennes to be the most likely course of action. The French command didn't react to these warnings, since they still suspected that an invasion through the Ardennes would be slow and difficult.

If the French command had instead reinforced the area, specifically with more anti-tank and anti-aircraft forces, they would've been in place for the German attack and could probably have held the position, especially since they had support from the Belgians in the area. In reality, the Belgians were overrun and the local French forces weren't equipped to deal with the number of tanks and aircraft they encountered. The Belgians retreated and then the French positions were overrun. If they'd effectively re-deployed forces to the area, the French could've counted on having numerically superior forces of heavier tanks than the German army. They'd also have a terrain advantage, fighting against German forces as they tried to emerge from the forest, rather than in an open position where the speed of the German tanks could be effectively used.

Basically, if the French had effectively countered the German armored divisions with their own, they could've won. Instead, their tanks were scattered thin across the Maginot line, which wasn't attacked, and had basically no impact on the battle.

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    $\begingroup$ Better still if the French had managed to keep it a secret that they had repositioned for an Ardennes fight. There'd be some Mon Calimari in an SS uniform going "It's a trap!" $\endgroup$ Commented Feb 1, 2018 at 23:48
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    $\begingroup$ The French command didn't react to these warnings, since they still suspected that an invasion through the Ardennes would be slow and difficult. ... French military command also made the statement that the Germans wouldn't use the same strategic plan twice (Germany attempted the same basic attack in WWI, of course), and French commanders somehow convinced themselves that the attack would come right through the heavily defended Maginot Line instead. Even without the benefit of hindsight, this was an obvious strategic blunder, for multiple reasons. $\endgroup$ Commented Feb 2, 2018 at 18:23
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    $\begingroup$ @HopelessN00b No, they were convinced that the Germans couldn't move tanks through the forests of the Ardennes. They were sort of right; the German Panzers got stuck in a traffic jam for ages in the forest. But because they were convinced the Germans wouldn't do it, they didn't prepare for it, and failed to react effectively to it. $\endgroup$
    – Semaphore
    Commented Feb 2, 2018 at 18:38
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    $\begingroup$ well it would have been better if Belgium had let the UK and France move to the prepared defence positions before the attack. $\endgroup$ Commented Feb 2, 2018 at 21:01
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    $\begingroup$ @Neuromancer - Belgium could not allow Allies to enter its territory ahead of war - Belgium was trying to stay neutral. $\endgroup$ Commented Feb 5, 2018 at 14:59

If you don't mind the change being natural rather than human based, have it rain for a few days after the initial attack. A good hard rainstorm for even two days would have kept the Luftewaffe from being nearly as effective, as they'd have less visibility and less obvious targets. It would also make take off and landing harder as many of the airfields were pressed earth or grass, if it got too wet they wouldn't be able to take off at all.

Rain would also slow down and wear out the soldiers as they march through mud in soaking wet clothes and packs. This in turn would slow down the tanks and armoured cars of the German army. Supplies wouldn't reach the front nearly as quickly further slowing them down.

Having a day or two to recover from the initial attack, would have given the French and English critical time to build up some defenses, regain control of units, and start using some of the soldiers on the Maginot Line as reinforcements.

It would still be a close thing, but with the Germans generally inferior weapons, and limited supply of advanced tanks and planes, they had to rely on speed and keeping the French and English off balance.

Considering the time of year rain is not uncommon, and rainstorms could last from a few hours to several days at a time. So having intermittent rainstorms of a few hours each over a week or two in northern and central France would hamper the German army fairly significantly without requiring a handwave.

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    $\begingroup$ Wet ammunition would also play a role here. Good idea, though I would be interested in more details on "Having a day or two to recover from the initial attack" and how well France could have reorganized, I'm somewhat of the impression that France would have needed more than a day or two to effectively respond. $\endgroup$
    – Twelfth
    Commented Feb 1, 2018 at 21:44
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    $\begingroup$ A week of rain would be best, but a day or two in the first week could do the trick. The main thing is to stop the panic from spreading any further so that people can take a few hours to take a breath find out what is happening and start defending. The main problem at that time was no one in command had any control, things moved faster than they could so any plans were obsolete as they were written. The lack of command sent the soldiers into a panic. If the troops had clear orders, even just to dig in and wait for reinforcements it would be a huge boost. $\endgroup$
    – Dan Clarke
    Commented Feb 1, 2018 at 22:44
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    $\begingroup$ The muddy roads strategy worked well for the Russians in 1941. The invasion of France would have shorter supply lines, so muddier roads would be required. $\endgroup$
    – SPavel
    Commented Feb 5, 2018 at 2:13
  • $\begingroup$ The muddier the roads the better, but they don't need to be swamps. As some other answers said, if the German commanders hadn't moved quite so fast, if a key battle had been slowed down, etc, things could have worked out better. The rain muddies the roads, slows the Germans down, and would give the French more time to prepare defenses around bridges or to bring them down. $\endgroup$
    – Dan Clarke
    Commented Feb 5, 2018 at 2:18
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    $\begingroup$ Could not help but think of this: youtu.be/PehCORojjtw. Great answer. $\endgroup$
    – jpmc26
    Commented Feb 5, 2018 at 23:16

The simplest change I can think of would be if the German army commanders had followed orders and stopped their advances as directed by central command.

Multiple times during the drive into France generals Rommel and Guderian encountered little to no resistance and advanced significantly farther than they were ordered to. They even went so far as to disobey stop orders, by moving their forces in so called "reconnaissance in force". These massive advances allowed them to attack the Maginot line from behind, causing confusion among the French forces, and meant that German forces were already occupying areas that the French army was trying to use to assemble for planned counterattacks.

Hitler's best military victories came when his directives were ignored. If the Nazi leadership had a tighter control on the German officers early in the war, and their orders were followed more closely, they would have lost out on many of the opportunities that the local commanders exploited.

If the German forces had stopped as ordered the French and British could have more easily moved their forces into place for a better defense and counter attack.

  • $\begingroup$ Wasn't such tighter control instrumental in the success of the D-Day invasion? I believe that several German commanders in France requested armored units (tanks) to halt the invasion at the beaches (or just beyond them), but they were unable to obtain authorization from the commanders in Germany. $\endgroup$
    – jpmc26
    Commented Feb 5, 2018 at 23:29
  • $\begingroup$ Excellent answer. Because it also rules out the usual "what if one of the assassination attempts on Hitler had succeeded" scenarios as a solution. Note that I am aware that there was no known assassination attempt on Hitler during the Battle of France (the question is about winning the Battle of France, not preventing it), but someone might have contemplated or even tried this (and have failed at an early stage). $\endgroup$
    – Klaws
    Commented Feb 6, 2018 at 13:57
  • $\begingroup$ one of these days I am going to write a time travel story where the time travelers have to save Hitler. As he gained more power as the war progressed his strategies and orders got so bad that he was probably the single most instrumental person in the allied victory. $\endgroup$
    – Josh King
    Commented Feb 6, 2018 at 15:00

As a single change...give Charles de Gaulle more influence over France in the early 1930's. Charles de Gaulle was a strong opponent of the Maginot mentality (potential he coined the term Maginot mentality) saying trench warfare would soon be obsolete and France's downfall would be because of it's dependency on these lines.

In his book "Toward a Professional Army", de Gaulle outlined what he described as the new warfare

He proposed mechanization of the infantry, with stress on an élite force of 100,000 men and 3,000 tanks. Ironically, German panzer units, so effectively employed in the invasion of France in 1940, used similar theories, while the French dispersed and wasted their armour. The book imagined tanks driving around the country like cavalry. De Gaulle's mentor Emile Mayer was somewhat more prophetic than he about the future importance of air power on the battlefield. Such an army would both compensate for France's population shortage, and be an efficient tool to enforce international law, particularly the Treaty of Versailles, which forbade Germany from rearming. He also thought it would be a precursor to a deeper national reorganisation, and wrote that "a master has to make his appearance...whose orders cannot be challenged – a man upheld by public opinion".[42]

Oddly, he very much outlined the tactics that would be used against France to conquer it...a little prophetic? Had France adopted to de Gualle's tactics earlier, they would have possessed the mobile force required to relocate and halt the Germans breach of the French defensive lines much more effectively. The key portion of this tactic is how the tanks were dispersed...ultimately the French dispersed their tanks relatively evenly along the line, when a mobile force of tanks would have been far more effective against the German invasion.


The actual answer is "pay attention". British military theorists like B. H. Liddell Hart and JFC Fuller had pretty much envisioned the elements of modern armoured and mechanized warfare in the closing days of WWI. "Plan 1919" was the conceptual means of defeating the Germans in a massive mechanized offensive in spring/summer 1919 using combined arms teams of tanks, "contact patrol" fighters to provide overhead cover and ground attack, and rapidly moving infantry and artillery to break through at selected points, exploit the breach and envelop the rear area. A draft of Plan 1919 can be read here

Sounds very familiar, right?

The British government even went to the extent of creating an experimental mechanized brigade and conducting a series of war-games and manoeuvres during the 1920's to test and refine these ideas. Given the technology of the time and financial constraints, the brigade was disbanded and shelved, but detailed reporting was available, and eagerly consumed by such luminaries as Heinz Guderian, Mikhail Tukhachevsky and Charles de Gaulle, and implemented by the German Army and (until the purges) the Red Army as well.

If the British Army had persevered with their experimentation of armoured and mechanized forces, even in the face of government indifference or cost cutting (for example, the Army could have chosen to close out other units, or do other cost cutting measures), they could either have had an integrated combined arms force of their own to oppose the German Panzers, or at least had corporate knowledge and been familiarized by constant training in how to defend against armoured and mechanized forces. The example of the British would likely have had an effect on the French General Staff, and they might have adopted a more comprehensive combined arms approach to warfare as well. It is often overlooked that the French actually had more tanks than the Germans at the start of WWII, and in many respects, French tanks were superior to their German counterparts (although the crew arrangements of French tanks were a serious weakness).

Familiarization with British practice would have impressed the need for better crew communications and tank layout on the French, as well as preventing the French from dispersing their tank forces in "penny packets" among Infantry formations. (In the real timeline, the British and forgotten many of the lessons of the 1920 era experimental brigade, and also designed tanks to be dispersed among the Infantry). Large numbers of more and better French tanks combined with an effective doctrine for their use would have seriously complicated German planning and operations, and an effective British mechanized force operating in the Western flank probably would have persuaded the Germans that their plan was not viable.

So in the end, what stopped the British and French from winning the battles and the campaign in 1940 was forgetting or ignoring the hard learned lessons of WWI and the lessons of the experimental armoured Brigade in the 1920's.


This is a nice breath of fresh air, usually we tend to focus on how nazi-Germany could've won the air.

Now, you're correct that the German plan to invade France and the low countries was by no means guaranteed. It was deemed too risky by most of the German high command and in fact was not the original plan the German military had in mind (whether the Mechelen incident influenced the change to the more risky thrust through the Ardennes is disputed). Even with outdated tactics and doctrine, the Allies still had a good chance of defeating the German attack. Their tanks were of better quality (though dispersed) and they had more manpower. Only the luftwaffe held the upper hand over their Allied counterparts - this military arm would prove vital during the battle of France.

the battle of Sedan goes more poorly for the Germans

Capturing Sedan and the bridges was a vital part of the German plan and this was where the main thrust would take place. Strategic success or defeat depended on the critical battle of Sedan. The French defenders they faced were mostly of poor quality (the best divisions had been sent to Belgium). Still, if things had gone slightly differently, the French could have delayed or perhaps even stalled the German advance, allowing strategic reserves to be pulled back from Belgium. The panic of Bulson (in which elements of 55th division fled because of a false report that claimed German tanks had already penetrated to as far as Bulson) was one such avoidable event. Or perhaps the aircraft that the British & French threw at the bridges over the Meuse river (where Luftwaffe fighters were swarming in enormous numbers) could have scored a chance hit, blowing up vital bridges and delaying the German advance. If the Allies had gained more time, they could have consolidated their defences and perhaps avoid encirclement and destruction.

The Allies adopt different war plans

There were several plans as to how the French and the British would respond to a breach of Belgian (and Dutch) neutrality by the Germans. These included plan E, plan D, plan D + the Breda variant and a plan which involved camping on the French north-eastern frontier.

  • Plan E: advance to the Eschaut river. This was the first plan, in which the Belgian armies would retreat westwards while the BEF swung into Western Holland. This plan assumed that the Belgians would not be able to hold their positions and was a more cautious plan than the plan D later adopted.
  • Plan D: advance to the Dyle river (further inland). This had many (perceived) benefits. It meant that the Allied forces would bring the fight further away from France as well as covering more Belgian territory.
  • Breda variant: this included defending Holland using French strategic reserves. Doing this would ensure the addition of 10 Dutch divisions but it also diverted strategic reserves
  • posting the French army on the French frontier. This basically meant abandoning Belgium - this was diplomatically not feasible, obviously.

Gamelin settled for plan D + the Breda variant. If he hadn't extended his forces so far forward, perhaps the war would have gone differently. The strategic French reserves certainly could've come in handy. Indeed, the Allies were initially rather unsure if they could reach the Dyle river before the Germans did (especially after witnessing the battle of Poland). The BEF was also not all too keen on entering Belgium. Only later, with reports of the Belgians and the Dutch constructing defences and an improved confidence in Allied strength and equipment, did Gamelin adopt plan D.

  • $\begingroup$ Maybe mention what the "BEF" is so this is a little easier for those not familiar with the term. $\endgroup$
    – Almo
    Commented Feb 5, 2018 at 16:26

Failure of German propaganda

The French Army in northern France outnumbered the German invasion force, and was fighting a defensive battle on it's home turf, plentifully equipped, and surrounded by supportive French civilians. France fielded 104 full divisions, and had a 50% advantage in tanks, artillery, and trucks.

However, three years of persistent, excellent German propaganda had demoralized the force at all levels. The French Prime Minister phoned Churchill and said 'We are beaten' on the sixth day, long before the actual outcome was decided, and four full weeks before the German Army entered Paris.

Demoralized leadership is less likely to analyze correctly, to innovate, to judge risk properly, to demand achievement from their subordinates...and more willing to accept poor performance and mission failure.

  • $\begingroup$ Haven't more novel employment of the equipment was more decisive? While French had equipment advantage it was dispersed as opposed to specialized Panzer divisions and Blitzkrieg tactic. I'm not sure how effectively deployed AA was but quick search shows that Ju 87 was deployed effectively making the ground equipment advantage null. $\endgroup$ Commented Feb 2, 2018 at 5:35
  • $\begingroup$ @MaciejPiechotka added paragraph #3 to (indirectly) address your concern. Not going to debate comparative advantage from one particular weapon or another - it's irrelevant. Had the French leadership felt that they could win, that they wanted to win, they would have found a clever, bloody way to do so with the assets they had. Others did. $\endgroup$
    – user535733
    Commented Feb 2, 2018 at 12:50
  • $\begingroup$ Also, might help if the French Prime Minister's mistress isn't a pro-German countess. Or, if you want to go the other way, her attempt to knife Churchill succeeded... $\endgroup$ Commented Feb 2, 2018 at 16:45
  • $\begingroup$ Agreed, but in the context of his saying "we are beaten" so soon, you have to wonder... $\endgroup$ Commented Feb 2, 2018 at 19:43
  • $\begingroup$ @BrianDrummond politely disagree. I think quote is a famous example of a general attitude among a large group of folks. I'm using it as a symbol, not a strategic decision point. I think the mistress is interesting, but not important to this particular question. $\endgroup$
    – user535733
    Commented Feb 2, 2018 at 20:16

Better French organisation of their armoured forces

The French Army had more and better tanks than the German (at least 3,383 to the German 2,445), but decided to disperse them throughout their positions in what were known as "penny packets" to support the infantry.

This negated their numerical advantage, and allowed the German Panzer forces to achieve local superiority where it mattered.

Keeping their armoured divisions concentrated would have allowed for swift counterattacks which would, at the very least, have slowed down the German attack for long enough for the Allie's superiority in men, tanks and guns to be brought to bear.

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    $\begingroup$ A couple of armoured divisions with supporting infantry could have cut Guderians supply lines. If only for a few days, the attack would grind to a halt and the French could have reorganized. $\endgroup$ Commented Feb 2, 2018 at 16:17

One thing is missing:

The Mechelen Incident never happens.

The initial plan for the German invasion of France was a frontal attack through the low countries into Northern France, just as in 1914. Furthermore, the idea was to start it much earlier than the 'real history' battle - shortly after the conclusion of the invasion of Poland, the idea being to catch the Allies unprepared. First it was delayed, then the plans were leaked in the above incident, causing a rethink and the invention of the Sedan concept.

So what happens in this original plan? The German army crashes into Belgium and Holland in December 1939.. in the middle of winter, and, interestingly with much lower ammunition reserves. No doubt Holland still falls, and much of Belgium, but the weather makes the advance slower and neuters the Stukas; the German armour finds itself fighting head on battles against British Matilda IIs and French Char-1B tanks, which completely outclass them. Going into 1940, Germany never gets the chance to concentrate all her Armour into a single strike.

The result is a stalemate, with a front line forming in similar battlegrounds to WWI. Except that the German economy is relatively much weaker than before; ironically it took the fall of France to put the German army on wheels - captured French equipment played a significant part at the start of Barbarossa.

Italy sees how things are going and stays very quiet.

By 1941, Germany is in a state of collapse. The Luftwaffe has been ground down in battles with the RAF and improved French planes; the Panzer arm is struggling against the numbers that the allies can put into the field, and the economy is disintegrating (in the 'real war', conquered France provided a lot of economic support to Germany as well). Seeing the writing on the wall, and with the Eastern border creaking ominously, the General Staff depose Hitler and announce an armistice.


Have the French invade Germany when Germany was invading Poland. France did send troops in and met little resistance, only to pull them back. Hitler really did bet everything assuming France would not act. He concentrated his forces on Poland and left little to defend Germany.


There are a lots of small ways the French could have made a difference.

My favourite: blow the bridges near Eben-Emael, on the Belgian-German border. At the height of the invasion into Belgium these bridges carried more then 100 trains a day. Without this supply / support any attack would peter out.

Mind that at this point in the war the Germans used a lot of foot troops and horses. Very little units had trucks. Most transport was done by rails.

If you want to try for bigger changes, do try Hearts of Iron 4, or the earlier versions. It is quite possible to hold the German advance in that game, though not easy.


In his book, Blitzed: Drugs in the Third Reich, Norman Ohler claims that German soldiers during the Blitzkrieg were high on methamphetamines, which improved their stamina, etc. Perhaps if those drugs had not been invented, had been contaminated, or unavailable, or if there had been a problem of overdosing, then they would not have fared as well.

  • $\begingroup$ You're referring to Pervitin. AFAIK it was indeed a vital part of the bombing of London, for example: the pilots were very tired after the long flight over the sea and used Pervitin to be able to perform their mission. $\endgroup$
    – DarkDust
    Commented Feb 5, 2018 at 12:28

When the German army was driving through the Ardennes French reconnaissance airplanes did spot them. There is a bit of a debate on what happened with that crucial information after that. Lets say instead of the information not being put to use the French Air Force concentrated their efforts on the route the German army was taking. With the tanks concentrated in a little area that would of been a great chance to reduce their numbers. Another angle is after the war the Germans who were there reported their logistic were actually not very good. Their tanks relied to a good extent on captured French gasoline. Even to the point of just using French gas stations. So if someone had just went before the German army and destroyed the gasoline supplies.


There are many components to the western front situation, so I'll recoup some:

1/ After WW1 the French were unwilling to go to any other war, since the bleeding was so terrible for them

2/ The British Army was as usual a joke, with the British Navy and Airforce being the sole expression of British military capabilities, especially the Navy

3/ While the German Army was woefully underequipped compared to the French, it had succeeded in drastically evolving from the WW1 mindset, where trenches and massive artillery usage were the deciding factors of the war. The French meanwhile had not.

(it is not very well known, but all the way to the battle of France and during the totality of the German-Polish war, thr majority of the German army was relying on horses, not cars or tanks. Most of the artillery in 1940 was still carried around by horses and not modern weaponry)

Counting on point 1, I would first assume that the French would not attack German territory no matter what.

I've heard rumors of the French Army being pressured by the British to not enter Germany under threat of seeing their oil supply lines cut (as those were almost entirely under British control back then), because the British plan would've been, as is typical with them, to sink their "ally" and enemy altogether by ensuring that both sides remain about as strong, thus dragging on the war to impoverish both.

However even if you take these rumours seriously, the French would never have attacked any way.

The French Third Republic was a weak system where governments changed often and party alliances were necessary in all situations, and popularity for the war was so low that when the war was started, the speech made in the National Assembly did not even dare to contain the word "War", simply requesting "extraordinary military credits" rather than demanding national mobilisation.

The French, all too scared after the bloodbath of the Great War, would've probably stayed put and tried to shoo the German away with their big Maginot Line anyway.

With that option out of the way, there are a few ideas:

Before the War even started, it was imperative for the French High Command to evolve with the times. Tanks weren't the WW1 tanks, and allowed for high power assaults that trenches wouldn't be able to hold back anymore. Aviation had also greatly evolved and needed to be taken along infantry and armor, which is what the Germans did. The Blitzkrieg was a fairly simple but modern tactic of uniting infantry with armor along with air support, whereas the outdated vision was to use them separately. The French did not understand the value of mixing all three, except by some like then Colonel De Gaulle, or Marc Bloch:

During The Phony War (39 to May 40), more military pressure should have been put by both British and French on the German border. While the Germans had almost all their divisions in Poland, France alone could muster about 80 divisions against the 30 German divisions that were guarding the border. Even if you don't consider a full on assault, skirmishes and pressuring the enemy was tremendously important, especially when the Germans were advancing quickly in Poland and needed to be stalled for the Polish Army to recover footing (at the end of the German-Polish war, 80% of Polish soldiers were still standing, but it was a military checkmate because the Germans had taken vital parts of the nation due to their speed and execution with the Blitzkrieg tactics).

In that same period, had Sweden not decided to simply let the German Army walk freely to Norway, the stalling of the Germans could have prevented them from getting full control of Norway before the British-French expeditionary corps had taken control themselves.

During the War itself:

  • The Belgian line fell almost immediately, prompting the French to send their best equipped and manned army there, along with the British Expeditionary Force. Had the Belgians held longer, the support force might've been able to create a frontline and stall the Germans there.

  • The Germans pierced through the Ardennes and made a pincer move on that army. Had the Ardennes been properly seen as a possible entry point and guarded, the pincer would never have worked.

  • The British immediately decided to run and abandoned their defense positions, along with a huge amount of equipment, to run for Dunkerque and then home. Had they not abandoned the fight as soon as the battle looked awry, then had they not abandoned their equipment without destroying it to save their men, and had they not made building a frontline even more difficult by running away in the first place, the 1st French army might not have fallen so quickly defending the British retreat. Although to be honest by then the situation was very dire anyway.

The rest is a long string of rather pitiful but unavoidable situations.

The French had superior weaponry in every way, but lacked both modern tactics and proper communications. I don't know why communications were so poor, but there were actual articles in the news about 4 communist sympathisers that were tried and executed for sabotaging tank radios in the factory(since back then, Hitler and Stalin were allies). How prevalent was the sabotage, I do not know either.

But in general, the Germans worked with efficiency, mixed troops, and a goal to advance as fast as possible so as to continously hustle french forces and never let them form a frontline. It worked so well because the french were constantly at a loss as to where the frontline was, while it moved every day, they sent infantry or tanks alone against mixed troops that would just break through any defense fairly quickly, and they did not have powerful enough communications to ever mount a solid counterattack.

I hypothesised that had the Belgian Front held, or had the Ardennes been properly defended, or had the British held their line, things would have been different, but in reality I am not so optimistic.

The fact is that the Blitzkrieg will only be properly countered with somewhat modernised tactics only by 1943, after Stalingrad. From 1939 to 1942, the only thing that saved anyone from the German Army was Winter. Nothing else stood, except the Channel I suppose. To last longer against the German forces was to win in the long run, essentially, and neither Polish, nor French, nor British, nor the USSR, stood the Blitzkrieg in its prime. Let me remind you that Moscow was only saved by Winter, with very little land left to conquer in 41, and Stalingrad was actually taken before being turned into a mass grave during the winter of 42.

I've also let out a ton of details as this post is already extremely long, such as the replacement of the Top General of the French Army at the worst possible time, or the fact that after the 1st Army was lost in the Dunkerque pocket, the French were pretty much left with their pants down and really couldn't stop the German Army no matter what anymore since the other forces were less well equipped, experienced, and France had lost a lot of manpower after their best army was gone and a ton of British material was left freely to the Germans.

But to me the real problem will remain the outdated tactics, misunderstanding about the nature of the war, where positionment wasn't as important as speed, where mixed units weren't even considered, and where the French High Command was completely incompetent at realising its mistakes from start to finish. Heavy military reforms before and during the war, or stalling tactics like harassment, were absolutely necessary and would've turned the tide in many ways. But since neither were done, the only important thing was time. The Germans were so advanced militarily despite inferior heavy weaponry that it took 3 years for anyone to catch up and beat them head on.


If I have time I’ll cite some sources later and get specific number. Something not mentioned yet is to start the war early. Stand up to Germany before Poland. Stan up to them in March of 39 with the invasion of Czechoslovakia. The balance of mechanized forces and specifically of air forces would have been more in the allies favor at that moment.


I have repeatedly wargamed this battle and in most cases, as the allies, have achieve a much better result than the historical one.

In the quest for historical accuracy there was only one way to achieve the dismal results of May 1940. If the French player is given information one day old the results end up looking pretty much like the historical ones.

This reflects the failure of command and communication in the French army. The French were fighting the last war, their command communication control and information network was setup to fight a static war not a manoeuvre war.

This is reflected in the command styles. The French army was commanded by general officers a long way behind the front. First information had to get them, they had to make decisions on that already old information and then get orders to the people doing the fighting.

The German general officers of the Panzer Divisions that exploited the breakthroughs fought near the front of their Divisions. They could make rapid and accurate decisions on where and when to apply force to destroy their enemies will to fight and to exploit weakness, caused in many cases by their enemies reactions to old information.

There are many ways to improve the outcome of the battle for France. Worthy of mention is the concentration of the superior French tank forces into a proper mobile reserve capable of defeating the German penetrations. My choice would be to fix the C3I problem, get the allied generals out of their Chateauxs and onto the front line where they can see what is really happening in real time.

  • 1
    $\begingroup$ I was going to write my own answer, but perhaps it is better to expand upon this one. On the subject of communication, If the French had invested in radios, they would have relied less on motorcycle messengers who then didn't make it. There were a lot of the French forces that just didn't receive their orders and so were not ready or in position to fight. The French forces were also spread out, with a distribution of force, rather than concentrated force. If they had co-ordinated and brought their forces together, they could have formed an effective defense... $\endgroup$
    – Baldrickk
    Commented Feb 6, 2018 at 10:31
  • $\begingroup$ ...and counter-attacked. The B1 Bis for example was at the time the world's most advanced tank and should have been perfectly capable of fighting off the Pz I and Pz IIs used by the German forces at the time - as long as they were not isolated as they were. $\endgroup$
    – Baldrickk
    Commented Feb 6, 2018 at 10:41

After many good answers and further research, it seems that, by all accounts, the Allies should have won, surprisingly enough. The Nazis won thanks to a ridiculous string of coincidences that would have had put any reader out of the story, had it be fictional.

At the end of WWI, France had the most modern army in the world. A massive pool of truck instead of reliance on trains for moving troops, the biggest air force of the planet, troops being equipped with semi-automatic rifles and a massive number of LMGs, turreted tanks and combined operations... And while Great Britain put comparatively more efforts into its navy, its army was about as advanced and had even started working on APC vehicles.

How do we get from this to such a debacle?

The post-WWI years

After war, both nations knew they needed a rearmament program, to thoroughly modernize according to the lessons learned form the war. Of course, rearmament programs are expensive, and when the deadly, exhausting, impossibly costly war that was supposed to be The Last One is just finished, some people may think that diverting funds sorely needed for reconstruction to the army is not the best idea.

In the aftermath, the British stop pursuing combined arms doctrines, which are slowly forgotten. And the general Estienne, father of the French combined arms doctrine, dies early before having time to further develop his ideas, resulting in the same loss.

tl;dr: Had either not let their armies decay, especially doctrine-wise, they would have been prepared against the new German tactics and blunt their advance.

Britain was focused on trying to hold together a dying Empire, and the focus on the navy and on rebuilding the economy left the army deprioritised, and it went back to a smaller expeditionary force, not unlike it was pre-war, even if its rearmament program was somewhat less disrupted.

Meanwhile, France starts its complete rearmament program. It develops a rather excellent light machine gun, then starts working on a new semi-automatic rifle and... thing peter out, especially after the 1929 crisis. Then new left-wing government, focused on social progress but openly contemptible of the traditionally right-wing army, cuts military funds as much as possible. A French head of state of the time goes as far as declaring that "If I could, the army would not get one centime in peace time".

Even worse, fearing the potential influence of the army, they change the appointment system for top officers: instead of picking from a list compiled by high command based on competence, they are now directly nominated, based on political affiliation. But wait, you might say, wasn't that exactly what had happened before WWI? Didn't France have to fire a third of its generals early in WWI because of that? Didn't they know that was a bloody stupid idea from experience? Yes they did, but remember, the priority was to make sure the army was not a political menace. And anyway, who would be insane enough to start another world way, after all?

As the threat of a new war loomed, France picked the rearmament program back up, but it was too little too late. They had great planes, but not enough - and the newest model was basically at the prototype stage and sent to the front from the factory. They had great defensive tanks, but with flaws not yet kinked out. They had great sub-machine guns, but only a few hundreds had time to reach the troops. They had great rifles, but had only time to equip troops with a bolt-action version planned for rear-echelon troops. The semi-automatic version, which would have been one of the best rifle in the entire war, was barely complete, and didn't even have time to leave the factory (fortunately, they did manage to hide its existence to subsequent German occupation forces).

tl;dr: Had the French government at the time not seen the army as a political enemy and cripple its high command, it could have developed new doctrines and efficiently respond to new German tactics.

The appeasement politic

Interwar France and Britain have been criticised a lot for their appeasement politic, believing that if enough concessions were to be made to Germany, they wouldn't do something as stupid as start another war. Had they read Mein Kampf, they would never have believed Hitler's words about wanting peace. (Then again, that book is allegedly so badly written to be painful.)

It is difficult to imagine what an early war would have looked like, but Germany probably was more unprepared than others. Had the Allies (possibly without Great Britain) gone to war over Czechoslovakia, it may have gone badly for Germany. But this would have required a significantly different political climate at least in France if not in Britain as well, so this is somewhat difficult to imagine it happen at that point.

However, had the Franco-Soviet 1935 treaty held, Germany would never had stood a chance in a war. Had Stalin compromised over not sending troops on Polish territory, or had France been less eager to appease Germany, the Soviet may have very well ended up with the Allied at the start of the war.

tl;dr: Had the alliance with the Soviet worked out, it would have been a race to Berlin five years early.

Speaking of Poland, they did quite better than is commonly believed (mostly based on Nazi propaganda, as it happens). But as to not, ah, provoke Germany, France and Britain had stopped Poland to fully mobilize, considerably hampering its war effort against German and then Soviet attack.

Even worse, its strategy was to hold long enough for the French army to launch an offensive across the Rhine, and for the British air force to launch a bombing campaign against Germany. Neither were actually prepared to conduct such operation, and had assumed Germany would be deterred simply by the threat. France launched a probing attack, met no resistance but decided to withdraw behind its fortification. Britain sent a few token planes, met no resistance but decided to stop further attacks. However, even unprepared (which they shouldn't have been), attacks against the undefended western Germany while its army was stuck in Poland could have stuck a heavy blow, either stopping it from finishing Poland or at least seriously weakening for the counteroffensive.

Also the offensive happened right before Poland would receive thousands of modern planes for its air force. I suspect Germany wanted to attack before that, as it would have seriously challenged the Luftwaffe.

tl;dr: Had the Allies been prepared to support Poland, they could have dealt a potentially fatal blow to Germany.

Defensive strategy

Nonetheless, as the years pass by, with more and more nations falling toward extremism, it had become clear that a new European war could happen again. The "twenty years of armistice", as Field Marshal Foch had called the Versailles treaty, were coming to an end.

Britain could count on the Channel, its navy, its air force and an alliance with several continental powers to prevent a war from reaching its homeland. France, however, was right next to the biggest potential threat, a revanchist Germany that could field twice as many men, and that had already proved its capabilities at massive industrial war. Which is why they did the logical thing and developed the Maginot Line.

But wasn't the Maginot Line a terrible idea that miserably failed? No, in fact it was a great idea and, when used properly, it worked exactly as advertised. (See below as for how it was not used properly.) It was the brainchild of WWI veteran Philippe Pétain who, despite some, ah, unfortunate political decisions later (again, see below), had still been one of the best generals of WWI - so not an idiot, and not an idiotic idea.

The Maginot Line was an impassable line of fortifications, estimated to hold with a contingent against an army fifty times more numerous. And, contrary to much later rumours, France was perfectly aware that the Germans would push through Belgium - and so was Belgium, in fact, which is why it was part of an alliance with France and Great Britain. Belgium was to build its own equally impassable Meuse–Albert line.

The problem is, impassable fortifications cost a lot, and Belgium simply didn't have enough money. So they asked France to lend them enough funds for the project. Which France declined (see above for why they would do such a thing). Which is why the Meuse-Albert line was delayed and scaled back. At the onset of the war, it was clear that the Belgian army wouldn't be big enough to hold a determined German push at its border.

tl;dr: Had France lent the money to Belgium, no German army could have crossed their eastern border.

Nevertheless, with the bulk of the French army and the British Expeditionary Force to back them up, it would still be enough to stop a German attack. As long as they were deployed in advance, that is. But if tensions rose, as allied nations, of course this is exactly what would happen.

But then the remilitarisation of the Rhénanie happened, and neither France nor Britain reacted, not wanting to declare war on Germany over internal troop movements. After all, they simply wanted to legitimately be able to defend themselves, right?

Belgium saw this appeasement politic as a sign that it couldn't count on the Allies, and thus left the alliance, hoping that neutrality would avoid it to be caught in the next war. Which meant not having foreign troops on its territory. Which meant that when Germany attacked, French and British had to rush from the French border to the frontline, losing much of their defensive advantage, and the easier to defend eastern Belgium being already overrun when they arrived. From there to Paris, there were only flat, hard to defend plains.

tl;dr: Had Belgium not left the Allied for neutrality, the German army would have been stopped, or at least considerably weakened, at its eastern border by the Allied forces.

But then, why didn't the French simply extend the Maginot line? Actually, they did. But two years were simply far too short a time to build such fortifications, especially on flat terrain.

The Ardennes gambit

Now, the German plan was to repeat the Schlieffen plan that had nearly worked so well in the previous war: launch a massive fast offensive through Belgium and run for Paris to knock France out of the war early. Sure, it had failed last time, but it had worked the time before that. And Germany didn't really have other options anyway.

At least, this was the plan before it fell in the hands of Belgian intelligence, when a German courrier plane randomly crashed in Belgium, carrying said plans. And while the Belgians tried their best to make it look like the whole thing had burned, the Germans knew to be better safe than sorry: they needed a backup plan.

So they did what would otherwise have been an idea worthy of the Chemin des Dames offensive in its utter stupidity: send two tank corps through the Ardennes forest.

Now, the French knew perfectly well that an Ardennes tank offensive was possible, and that a tank army could cross it in two days. Specifically, Maxime Weigand, possibly the most underrated general of the XXe century, had warned François Gamelin, the French chief of staff, of this.

(It was also Weigand that told Charles de Gaulle that his idea of a small, mobile professional army of a hundred thousand men for defense would simply not work - probably because the British had done the exact same thing during WWI and it had been ground down to oblivion in a few months, and thus earning De Gaulle's unending antipathy. But this is a story for another time.)

Once entrenched in the Ardennes forest, even a modest force could have stopped a tank offensive. Tanks offensives are meant for flat terrain: forests make it easy to ambush even big armored forces, and once a few tanks are burning on either side, can easily become death traps.

Unfortunately, as noted above, top officers weren't named for their skills anymore, and Gamelin was a courtier but not a good general. Which is how he ignored both warnings not only from Weigand, but also from French intelligence in Germany about their innovative light tank tactics and training.

tl;dr: Had Gamelin actually listened to his best general or his detailed intelligence reports, he would have easily destroyed the Ardennes tank offensive with a few well-entrenched forces.

But then, even without opposition, having two tanks corps cross a forest like the Ardennes is no trivial task. In short order, tank columns turned into giant traffic jams, easily seen by French aerial reconnaissance.

When receiving such reports, however, the officer in charge of defending the sector dismissed them as "a few scout cars". So the air scouts went back with tankers on board their planes, to identify the tank models and make unambiguous, detailed reports of the tank force.

No matter, the officer dismissed the new reports. When the French air force asked him if he needed any support, he answered none whatsoever. One may wonder if he was that incompetent, or if it wasn't actual treason. Had the air force been sent to bomb the piled up tanks, it would have been a massacre. The few survivors to make it would have been easily stopped by even a light force, had it been forewarned.

tl;dr: Had the officer in charge of the Ardennes defense not been terminally incompetent/a traitor, or had someone gone over his head (or executed him for treason), German tanks would never have made it out of the Ardennes.

The Battle of Belgium

The Belgian lines breached, the Allied forces on the back foot, and now a tank force emerging from the Ardenne to envelop them. As in 1914 the French government finally pulled itself together, fired the incompetent, politically appointed generals and let actually competent ones do the job instead and save the day. Namely, they pulled the aforementioned Weigand from retirement and gave him Gamelin's job as chief of staff.

Now, you would think Weigand was the right man for the job: respected by friends and foes alike, right hand man of Allied supreme commander Ferdiannd Foch during WWI, architect of the Warsaw Miracle, absolute légaliste with an unwavering loyalty to democracy and to the Republic. But with the entire French army disorganised, lacking radios and fast-moving forces, about to be encircled, what could even he do?

What he did, was to understand that the main German armored push was overextended, and that there was an opportunity: the French army would counter-attack in a pincer move, hammering the German forces against the British and Belgian anvil, and cut off the spearhead. British high command agreed with the plan, and so do modern experts, who argue that it would have indeed worked.

And then the British ran away.

Specifically, John Gort, commanding the British forces on the continent, panicked and ordered his army to rout towards Dunkerque - leaving behind piles of equipment for the Germans to take instead of properly destroy it all, but destroying bridges, trapping the French and Belgian forces that would be forced to retreat later.

With their flank gone, there was no more hope of victory for the French and Belgian forces, so they started to retreat as well. Both fought hard - the French fighting retreat was especially brutal, taking the highest relative death toll of all the European armies of the early war. German general Heinz Guderian, would in fact call the battle of Stone one of the two worse he ever saw - along with freaking Stalingrad. In fact, the one thing that saved the British army (along with Hitler's tactical mistake at Dunkerque) was the French army standing against literally impossible odds for the entire retreat.

Note: remember that next time you hear about a (much more recent) surrending monkey joke or about the Miracle of Dunkerque: the British ran and only made it because the French stood and died. Not even the guys who invented the Polish lance cavalry charging panzers myth dared to mock the bravery of French soldiers. In fact, Hitler himself called them the best in the world after the Germans (of course), in the aftermath of Bir Hakeim. But again, this is a story for another time.

tl;dr: Had John Gort not panicked and the British stood their ground instead, the German advance would have been smashed by a pincer move, stopping the German advance.

For what of a fistful of nails

Had the German advance been blunted, things would have reverted to a 1914-again state: a grinding war with neither side capable of advancing. This would have pitted industrial and manpower reserves against each-other, and like for WWI, the Allies would have had the upper hand with access to the immense American industry. The Soviet Union may have somewhat balanced this by trading with Germany, but this is neither certain nor guaranteed to have lasted. (Soviet-directed Communist agents were executed in France for sabotaging planes, for example, so the Soviet Union was, at least initially, somewhat serious about their pact with the Germans.)

New weapons would have made a difference. Many northern French and Belgian cities may have been razed by artillery fire. New railway trains may have been used to destroy fortifications like on the Maginot line, but the enormous investment on those and on the follow-up force needed to have a chance to advance. As such, like in WWI, it is improbable (though not impossible) for the Germans to achieve victory that way.

In addition, and contrary to what many think, the Allied had the initial technological advantage. In fact, the reason later German tanks were so good was partly because of the French tech they got their hands on, and on the resources of the French had from their colonial empire, allowing for better alloys. Had the war become static, the Allies would have kept the technological advantage, especially with Hitler increasingly obsessed with wunderwaffen and the French armament program being finally completed and extended.

Given how fast it rebounded after the war, and as there were pre-war projects already, France may have been the first one to develop rockets and even jet engines. it may even have fielded ramjets, whose development were interrupted by the Occupation. They also had few wagons full of uranium ore that spent the entire Occupation pointedly forgotten in some railway depot, but while it would have considerably helped nuclear development, it is far from certain that the war would have lasted long enough for an atomic bomb to be finished.

tl;dr: Had the initial push been stopped, it is improbable that Germany could have won WWI-bis.


At this point, the French homeland was lost. There was next to nothing left between the German army and most of France, with indefensible open terrain in the way. But France was still not ready to give up. it had 150 000 surviving troops evacuated from Dunkerque. It had an army holding the Italians at bay in the Alpes. It had an oversea empire, from which colonial troops could be raised. It had a modern, rather powerful navy.

So the French government did the sensible thing, gave up the indefensible territory and prepared to move the capital to Algiers (as Algeria was considered more or less French homeland at the time). In this time of crisis, they decided to unearth this old Roman tradition: nominate an emergency ruler with dictatorial powers, so the slower democratic powers can be temporarily been bypassed for the duration of the crisis. After all, if it worked for the Romans...

So they chose the victorious chief of staff of WWI (Foch was the supreme commander of the allied forces at this point, which was not the chief of the French army), the Lion of Verdun, a national hero whose military skills had been well-proven: Field Marshall Philippe Pétain.

Unfortunately, he was also going senile and had never liked politicians to begin with. This was the "divine surprise" that fell on the lap of the far right, who seized the opportunity to take power in Pétain's name and stage a coup d'état. While officially called the "Nation Française", it would be remembered as the Vichy regime. In short order, being ideologically close to Germany and Italy but deeply anglophobes, they would sign an armistice (not a capitulation, because that would make the army lose face, a big no for a fascist regime) and nevermind the loss of half of France and basically becoming a puppet of Germany (even if officially neutral in the war).

Oh, remember the French navy? half of it was stuck in Toulon and, much later, scuttled itself so the Germans wouldn't get their hands on it. Another half was in Mers-el-Kebir, and the British murdered it with a surprise air attack, so (agian) the Germans could't get them - but the French sailors were actually busy scuttling said ships, so not only were they especially defenseless against a surprise attack from an ally, but even more died trapped in the ships.

So while the armistice was very unpopular for many French, many also felt betrayed by the British and decided that neither side was worth it anyway. Even then, and despite everyone (including the Allies) considering the Vichy regime as the legitimate French government, "Fighting France" (later Free France) was formed as a government in exile refusing to stop the fight. While only a few troops and colonies joined it, plus those forming Résistance groups in Vichy and occupied territory, they became increasingly popular and, in the case of Bir Hakeim, even instrumental in the war. But again, this is a story for another time.

tl;dr: Had the French government named the maybe too modest Weigand instead of Pétain, the French Republic would have kept fighting from Algiers.

And the Devil is laughing still

Now as this is Worldbuilding and not History, let's try to make sense of it. Because as it is, this is all too ridiculous to use in a story, nevermind that it actually happened.

So let's take this ridiculous chain of coincidences, and the fact that it suddenly started to fall apart everywhere. Add the countless failed assassination attempts against Hitler. Add that the Nazi regime was not simply evil, but Evil. They didn't just invade Europe, raze cities and murder countless civilians. They didn't simply have insane racial theories they actually attempted to put into practice, and allied with an equally monstrous regime on the other side of the world. But not only did they industrialize genocide (and yes, I am the first to be surprised that it has to be reminded nowadays), but they actually wore skulls as a symbol.

And the SS had a war song with those lyrics (translated, obviously):

"And the Devil laughs with us"
"Ha! ha! ha! ha! ha! ha! ha!"

Also Hitler was into occultism.

tl;dr: there is one obvious explanation: Hitler made a deal with the Devil.

Seriously, why don't more people use this in secret-history or alt-history works?


Strategic Depth

The French invested heavily in the Maginot line (and famously didn't extend it across the border with Belgium), and the Germans just blitzed right past it.

If the French had stationed their army throughout their country, the Germans would have had to fight for each city, and held men in reserve to hold the countryside, too.

  • 13
    $\begingroup$ The French didn't have enough of an army to do that. What everyone going on about the Maginot Line is forgetting it that it worked exactly as intended: a fortified border that the Germans wouldn't be insane enough to try and hit directly, forcing them into an area where they could be met by French and British mobile forces who could be concentrated instead of dispersed trying to defend an entire front from the Channel to the Swiss border. That worked perfectly: the problem was that the British and French screwed up the rest of it once they had the Germans going where they wanted. $\endgroup$ Commented Feb 1, 2018 at 21:18

The British held back some of their air forces for defense of the home island and withdrew others when the it seemed that the Fall of France was inevitable. This is usually considered a wise (though painful) move on the part of the British, one that made possible their later victory in the Battle of Britain. In an alternative history, what would have happened if the British increased their air forces in France, even to the point of denuding their own air defense? One version (and arguably the more plausible version) of the alternative history would have been that France would have fallen anyways, followed rapidly by a Britain which could no longer contest the Luftwaffe. On the other hand, just maybe if the British went all in with their air force then they could have bought time for French forces to regroup.


Get the French inside the German OODA loop

The French generals were veterans of WW1, so their thinking was for static warfare against a dug-in enemy. They set up shop well behind the lines and assumed that motorcycle dispatch riders would provide them with sufficiently timely information (source: "The World at War"). In the event the German doctrine provided German unit commanders with sufficient flexibility to exploit local advantages, and modern communication technology (especially radios) kept the rear echelon able to respond in a timely fashion. There is now some argument about the extent to which this was an official doctrine and the degree to which the Germans made it up as they went along ("No plan survives contact with the enemy"), but either way it was the crucial advantage.

The result was that during the Battle of France the French command repeatedly ordered "stop lines" to be created, only to learn that these lines had already been overrun before their orders arrived.

If the French had been using similar doctrine to the Germans then they would have been ready for a war of maneuver instead of a rerun of the WW1 trenches. This lesson has now been generalised (no pun intended) into the concept of the "OODA loop": Observe, Orient, Decide, Act. The point is that if you can do this faster than the enemy then you have a decisive advantage, because whatever the enemy does, you can be there ahead of them. In the Battle of France the French high command had a very long OODA loop, on the order of a day, while the German high command had a much shorter one. Hence the French were only able to react belatedly while the Germans took the initiative.


Breaking the ENIGMA

I think WWII had been significantly changed, if British intelligence were able to break the ENIGMA earlier. The ENIGMA was a cipher machine to encrypt military communication during WWII. The decryption key changed every hour, so it was almost impossible for the Allies to read the messages (because the key was written on a physical handtable and was very well protected). So if it was possible for a spy to extract that handtable without the Germans noticing, they could hear all military communications from the German, to predict any troop movements or tactics.

This is an abstract from Wikipedia:

The Enigma machines were a series of electro-mechanical rotor cipher machines developed and used in the early- to mid-20th century to protect commercial, diplomatic and military communication. Enigma was invented by the German engineer Arthur Scherbius at the end of World War I.[1] Early models were used commercially from the early 1920s, and adopted by military and government services of several countries, most notably Nazi Germany before and during World War II.[2] Several different Enigma models were produced, but the German military models, having a plugboard, were the most complex.[...] Though Enigma had some cryptographic weaknesses, in practice it was German procedural flaws, operator mistakes, failure to systematically introduce changes in encipherment procedures, and Allied capture of key tables and hardware that, during the war, enabled Allied cryptologists to succeed and "turned the tide" in the Allies' favour.[7][8]

Also look for: The Imitation Game

  • $\begingroup$ The Enigma key changed daily, not hourly. Also, the Polish actually did both of these things before the war — they were breaking Enigma, and anyway knew the keys thanks to a spy. But the spy stopped delivering, and the Germans upgraded Enigma by adding more wheels (enlarging the keyspace), shortly before the war. Polish intelligence could not afford to keep up, but handed all their research over to the allies, who had until then believed Enigma to be completely unbreakable. Still, it took some time to catch up. $\endgroup$
    – Lars H
    Commented Nov 17, 2020 at 18:37

To add to the earlier natural cause of rain I suggest something smaller like a plague or food poisoning.

If all the provisions had been tainted by Salmonella, Ergot, Dysentery, Cholera and Botulism (chance or with the aid of the resistance) and the fighting forces had been down to 25% for a week it would have made a lot of difference.


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