Modern warfare theory in a medieval setting

Question

Let's assume a medieval lord named Gary I of Flowers lives in a "Europe-ish" continent with no gun powder or magic. Somehow, he's aware about modern warfare theory. Maybe he found out a time-traveler who happened to be an expert in warfare (and nothing else!), or maybe he's just ahead of his time.

Gary is an excellent general of his times. He's adaptive, open minded, and well respected by his soldiers and knights. He also has plenty of time and gold to modify his army. There is no "culture shock" from any unconventional tactics Gary would use. At least for his men...

By modern warfare theory, I'm not talking about using modern equipment - Gary doesn't have the means nor the technical knowledge to produce those. I'm currently thinking about using principles, tactics, strategy and knowledge about warfare generals of the 21th century to master and adapt it to a medieval technology.

My question is, would modern warfare theory be useful to Gary against his enemies? How would his medieval army, tactics, and strategy change using only resources available at the time?

Of course, it may change society as a whole, and ends the Middle Age way sooner than expected, but I'm not interested in that. I want to focus on warfare and everything directly related.

The only question I found in this site related to mine is this one, Mechanized infantry of the medieval age , but it only focus on one thing. I know my question is very open and may be unclear. I would love to read any feedback.

Answer 1

Lots of excellent stuff here so here is my 2 cents.

One of the biggest "modern" warfare things that Lord Gary could adopt that was not very common is the concept of Meritocracy in his army.

Throughout history this always seems to present an odd dichotomy, as some of the most terrifying and effective Armies in history had at least a bit of this going on. "Hey, that guy over there always seems to keep most of his folks alive in an engagement and he kills a lot of the enemy, maybe we should promote him even if he isn't part of the aristocracy" There is even a story of Ghengiz Kahn not only promoting the bravest and best from his own forces, but bringing in an enemy who shot the Kahn's horse out from under him. Legend goes that Jubei the Arrow (as he became known) was a leader from an enemy tribe, and he got close enough to shoot Ghengiz Kahn's horse. When captured, Jubei remained defiant. Ghengiz then offered him a generalship.

The dichotomy happens in what seems to be times of peace, when the Generals who earned their spot lose some relevance and get supplanted by an entrenched aristocracy. For some reason, the nobles kept equating bloodline with skill in battle.

There are 2 other things he could learn from a modern military. Intelligence and Logistics, and why they are so dang important.

In the modern day, the command with the most and fastest information has a huge advantage. Dial that back to medieval times that means spies and innovative communication methods. Lord Gary should become nearly obsessive in his pursuit of methods of communication on and off the battlefield. Messenger birds, Dolphins, monkeys, smoke signals, Heliographs, semaphore, drums, bells, astral projection....anything at all that can send information quickly and accurately. Information is critical for all levels of the military. Lord Gary also needs some people who know what to do with the mess of information. As a bonus, if Gary develops a good spy network, he can supply the enemy with disinformation.

With Logistics, every army marches on it's stomach. Even though foraging was par for the course in medieval times, Lord Gary wants to insulate his army from the vagaries of the countryside as much as possible. That means a solid baggage train. It means planning, it means men moving at the speed of the luggage. It means fortifying supply stops. It also means another more modern military take. Men need rest along the way. You cannot push them to absolute exhaustion on the march and then expect them to perform when they get there. Another part of the supply chain is quality. Gary should fund research into creating preserved and portable foodstuffs. Salted meats, beans, rice, root crops that last. In addition, part of the supply chain should involve knowing the location of water sources ahead of time and then what precautions to take like boiling the water when there is time.

Also under the heading of Logistics is the soldiers themselves. You can have a fantastic supply chain, but if you have crappy soldiers it won't be too successful. Before Lord Gary hits the road, his men need to be well trained. At home, just about everyone who can hold a spear should train with them periodically. Make it a universal requirement. That way Lord Gary's pool of available men will all at least have a baseline of training. Those that volunteer or are drafted will get a bunch of extra training before setting out. They can also drill everyday while on the march. The US military trains extensively and consistently. Make it a part of the daily routine at home and while underway.

Lord Gary seems like a smart guy. All hail Lord Gary.

Edit: the comments got me thinking about something. Another military concept that would help Lord Gary keep a top notch military would be to keep a skeletal permanent military. Not enough to be counted as an overly large standing army, but enough to keep a consistent command structure in place so that when it becomes campaign season, you don't have as much of a settling in process at the start. In keeping with the Meritocracy concept, make this structure a PURE meritocracy, with the members being part of a landless aristocracy. It's a great great honor to serve in this capacity. Anyone, even a peasant can rise through the ranks in this structure. It could be coupled with a requirement that members not have land to manage, not marry so as to stop the heredity nonsense (at least not while serving), and have a life with a full pension in later years. This give a consistent command structure that will be resistant to some court intrigues.

Answer 2

The question shows a misunderstanding of why the Middle Ages were medieval. It's not that the people who lived in those times did not know any better. They did. In particular, they had good Roman books about military strategy, tactics and logistics; for example, they had and they actually read Vegetius's De re militari; the book was copied over and over, and any aspiring general read it: not less than 226 medieval manuscripts have survived, and it was one of the first books to be printed -- the first printed edition dates from 1473. (You can find the 1535 edition at Archive.org.)

The medievalness of medieval Europe does not come from lack of knowledge, it comes from the lack of funds and people. Medieval economy was extremely sluggish, and as a consequence the states were extremely poor; they simply could not afford standing armies of any reasonable size, they could not afford training more than a handful of men, they could not afford sustaining a war effort for more than a few months at best. And they did not have anywhere near enough men. The Crisis of the third century started an unstoppable population decline, and 6th century Plague of Justinian killed half the remaining people in Europe: it took almost a full millennium for the continent to recover the population levels it had in the second century.

The conclusion is that just having knowledge of logistics and planning is nowhere near enough. They did not have the economic and demographic base to use it.

Other civilizations did have the economic and demographic base, and they had access to the same knowledge. The Arabs established a great empire, and took over large parts of Europe -- remember that for the most part of the Middle Ages the Iberian peninsula was Muslim. The (Eastern) Roman empire remained a great power throughout most of the Middle Ages, resisting the rise of the Ottomans.

But the sad reality is that throughout the Middle Ages Western Europe was an economic backwater, which did not have the capacity to project force.

Answer 3

Honestly the 'modern' military theory that would give Lord Gary the biggest advantage would be modern attitudes towards hygiene. It was extremely common in the time period you're talking about for a force to lose more troops to dysentery and other diseases than they lost in actual combat.

By taking a very firm attitude towards latrine maintenance and ensuring supplies of clean water, Gary could gain some pretty massive advantages in terms of how much of his force would be combat-capable at any given time, and keep a lot more of his troops alive.

This falls into the same category as AlexP's answer as well in that this was something the Romans were quite good at, but the practice was lost for a millennium and a half.

The Roman army took great care to construct sanitary facilities and segregate them from water, food supplies and dining areas. When water was in short supply lime pits were used in the latrines.

A complex system of drains and sewers emptied into streams, rivers. Drinking water for soldiers and animals were taken from water upstream or separate from the waterway used for latrines. Wooden seats for latrines which were dug to a depth of ten feet were situated over the main sewer running round three sides of the building to discourage disease-carrying insects. A smaller channel of water, fed from the water tank was for washing sponges dipped in a mixture of water and acetum (vinegar) were used as toilet paper. Latrines also had basins for washing hands.

Indeed, this ultimately developed into honest-to-god combat medics, far earlier than you would have expected. The Byzantine Empire developed a system for evacuating the wounded from the battlefield that was superior to anything Europe came up with until WW1.

Historically, the advent of the first truly organised military medical systems which included evacuation capabilities was found in the army of the Byzantine Empire. Scribones, stationed a hundred meters behind the action, served as corpsmen with the mission of rescuing the wounded during battles. They were paid for each casualty they rescued. No similar formal evacuation system existed in Western Europe until the late 18th century.

Answer 4

There are several relevant Clausewitzian, Jominian, and Machiavellian concepts that would benefit Lord Gary. While some of these seem obvious to us, recall that most wisdom seems rather obvious in retrospect.

• Clausewitz: War is an extension of politics, and wars have political goals. Putting 'war' in the 'politics' box doesn't reduce war, it expands the toolbox tremendously for achieving Lord Gary's goals. You can achieve goals through war...or through intrigue, marriage, etc. You can also use combinations of tools to achieve goals.

• Jomini: Several Principles of War apply regardless of the technology: These principles vary a bit, but let's go with Objective, Offensive, Mass, Economy of Forces, Maneuver, Unity of Command, Security, Surprise, and Simplicity. This leads toward smaller, more mobile, better-synchronized combined arms operations.

• Machiavelli: Motivate your troops directly, rally your population, use written guidelines of conduct, empower lower-level commanders to innovate. This will minimize the intrigue in Lord Gary's court, and will enhance the power of the force.

Plus one bonus with multiple authors:

• Military Staffs, a method of organizing information and synchronizing effort. It prevents overwhelming Lord Gary (or his Field Marshall) with unnecessary detail at the wrong times for smart decision-making. One goal is to reduce the decision cycle, so Lord Gary's forces that seem otherwise-equal-to-a-foe are nevertheless more nimble, survivable, and powerful due to the more efficient information flow.

The tactical impact of this knowledge depends upon the resources Lord Gary is willing to bring AND upon their personality and preferences. If Lord Gary is willing to have influence (a measure of control) over neighbors, then ordinary, cheap intrigue might be enough. If Lord Gary is driven to exterminate the neighboring lords, erase the borders, crown himself King (or Emperor), then quite the bloody war may be likely...if he can afford the enormous cost.

Answer 5

would modern warfare theory be useful to Gary against his enemies? How would his medieval army, tactic, and strategy change using only resources available at the time?

I am not an expert of modern warfare, but I doubt what we call modern warfare would be of any use in middle ages. Let's look at some of the key points of modern warfare

• Aerial supremacy and projection of force: there are no airplanes in middle ages, nor ships big enough to serve as force projection
• Blitzkrieg: no mechanized infantry to apply it, nor air force to support it.
• Logistic: medieval war relied on raiding the local territories for resources. There was no supply chain from motherland
• Electronic communication and intelligence: well, this is obviously not achievable.
• Professional army: medieval army were either mercenaries or people borrowed to the soldier's job for the time of the war. Professional armies came much later.

Maybe some concepts about guerrilla and asymmetric warfare might be useful, though they might sound ethically unacceptable for the medieval standards.

Asymmetric warfare can describe a conflict in which the resources of two belligerents differ in essence and, in the struggle, interact and attempt to exploit each other's characteristic weaknesses. Such struggles often involve strategies and tactics of unconventional warfare, the weaker combatants attempting to use strategy to offset deficiencies in quantity or quality of their forces and equipment

The term is also frequently used to describe what is also called "guerrilla warfare", "insurgency", "counterinsurgency", "rebellion", "terrorism", and "counterterrorism", essentially violent conflict between a formal military and an informal, less equipped and supported, undermanned but resilient and motivated opponent. Asymmetric warfare is a form of irregular warfare.

Answer 6

Modern tactics would be probably of less use than knowing historical tactics. There were a bunch of effective ideas scattered across Middle ages and early Renaissance, that work with medieval resources. Just some ideas off the top of my head:

• Make your peasants performing some basic training all year long, so they are more fit and skilled when the time comes to levy them. English did that, so could you.
• When possible, provide some basic training (2-3 weeks) to your newly conscripted soldiers before moving out. While you can't afford that when you are attacked, nothing stops you from doing that before you raid your neighbour. It will reduce effective length of the campaign, but even basic formation training will do wonders when facing less organised opponents. Alternatively establish some military conscription duty (including organization) during those awful non-productive winter months and focus on even some of the defensive skills
• Recognise defensive power of pike formations. In our history, pike formations made a comeback at the start of 14th century; lasting well beyond the middle ages. You Lord Gary could make that comeback a couple centuries earlier, and be just as effective. The best way of not getting overrun by cavalry is using defensive pike formation together with a LOT of organization
• Recognise power of crossbows. Both pikes and crossbows were despised in medieval Europe because they disturbed societal order, allowing lowly peasants to take out a noble lord with ease. But taking out the enemy lord is immensely useful, as most medieval battles weren't fought to the last man, but to the point when one side breaks and starts running. Death of a commander or two was significantly more demoralising than both before and after Middle ages. Have a small group of elite crossbow snipers, and you can win many battles with little blood spilt.
• If you wage wars for a few years without major losses (especially if, as noted in other answers, you promote hygiene and provide better medicine), you will have some fairly experienced peasants on your hands. Then you can go cheeky and make combined-arms pike+crossbow formations a-la Spanish tercio or Swiss phalanx. Those will both terrify your enemies and cut your losses even further.

Answer 7

I'm no expert, but here's my 2 cents.

I think in terms of organization and logistics Gary would be ahead of the rest. If Gary knows modern warfare he might also know the entire history of warfare that happened after the middle ages.

Gary could take inspiration from the battle of Agincourt and deploy many longbowmen in his army for example. Another thing he could replicate is how the Dutch revolutionized war during their war for independence against Spain. He could drill his troops until they start working like an oiled machine (something that wasn't seen much during the middle ages), and he could perhaps deploy rows of crossbowmen doing the "shoot and retreat" tactic like the musketeers did back then (creating a continuous volley).

Maybe these things won't make a big difference or end up not working as well due to technological limitations. Other tactics might only work in rare situations, but in the end we can never know for certain. So it's all up to setting/location and the world you build of course. I do believe that there are many cool scenarios you could pull off with Gary, however you would have to look into certain historic battles to get a grasp of the tactics used and see if Gary could apply them.

Answer 8

It seems to me reading the existing fantastic answers that in order to successfully establish any sense of modern military tactics in medieval Europe you must first shore up the shamble that is medieval economics and production.

A society is built upon its lowest level and so that is where changes should be made. The vast majority of medieval populations were farmers, food production was so limited that nearly everyone during the dark ages had to produce some amount of food for themselves, whether they owned livestock or maintained a small vegetable garden. This is a large part of the reason why it was so hard to maintain a standing army.

Introducing modern crop rotations, irrigation, fertilization and plows would be a huge boon to farming. With these techniques food and livestock can be grown and bred year round with better output which would allow fewer farmers to support a much larger population.

Follow up this boost to food production with better transportation, roads and infrastructure to distribute the food and now your kingdom can reliably supply itself and build enough surplus that a standing army can be maintained and properly trained. Peasants can also take up more specialized professions such as becoming dedicated blacksmiths, wood workers, armorers and weaponsmiths to fuel your military might.

Answer 9

There have been a lot of good answers on where modern warfare theory can help, and where the technological limitations are overbearing. Eg. Logistical, manpower and financial issues of large warhosts and prolonged military campaigns.

I would like to point out the distinct differences between tactics, strategy and grand strategy. Eg. is your setting of individual lords in a feud war against each other or a larger military campaign? In the case of multiple lords within a war host, your lord's seniority would play a huge factor on whether he is allowed to have any influence on battle strategy or campaign grand strategy. This lack of autonomy during larger battle planning also neuters a lot of tactical enhancements.

Throwing you a lifeline though, historical sweeping military successes can often be decided on a few specific events/stratagems. Eg. Scipio swapping his unit formation in the Battle of Ilipa or George Washington's crossing of the Delaware River. So perhaps you can simply write in greater historical warfare awareness as Lord Gary's superpower.

Tactical reforms can be in the form of better understanding of siege, battle terrain selection or long distance communication/coordination (try sephamores or homing pigeons). ie. more organised war intelligence service activities. Your army only really needs to win one or two really decisive battles/routs to severely impact the enemy's available manpower. So the overall theme really is about finding force multipliers or stoking fate from the choice of the field of battle eg. Flamininus in the Battle of the Aous

If you really must have some mechanism that makes Lord Gary's army have a distinct tactical advantage, perhaps think of localised cultural gotcha like swiss mercenary style halberd/pikes (the key is stronger unit cohesion and ruthlessness/veterancy of individuals), large scale deployment of crossbowmen levies or pavise crossbowmen. Essentially an usurpation of the period's tactical norms.

Answer 10

To our modern minds, reading medieval military history can be quite puzzling as often the kings and armies involved don't behave as we'd expect them to if they were trying their hardest to "win the war" as we'd imagine they'd want to.

A modern theory of warfare is to seek out the enemy on the battlefield, destroy their army, leave them defenseless, and then capture their territory. By contrast in Medieval warfare the armies seem to regularly miss chances to force battle on their opponents, they fail to optimise their weapons systems to get maximum advantage, they spend inordinate amounts of time pursuing things other than battle like sieges and raids, and they often seem to wander around aimlessly rather than striking strategically at enemy territory.

Some of this is due to the logistic difficulties of the time as other answers have noted, but what has been missed is that the Medieval mind clearly has a different conception of what warfare is and how it should be properly done. What explains the difference is the importance of religion - unlike today, everybody in the Medieval World believed in God.

To the Medieval mind the outcome of battle is a direct judgment from God and therefore understandably Medieval rulers were often quite circumspect about seeking battle. Also Kings (and not just oneself but the rulers of rival kingdoms) were seen as having a divine right to rule ordained by God - so even when they fought it was restrained by a respect for the others authority. For example, when the English and French fought the Hundred Years War, they were not trying to "invade" or "conquer" each other as they did when they later fought the Napoleonic Wars. In Medieval times the aims and means were more subtle (at least when Christian rulers were fighting each other...)

I would argue that transferring a modern sensibility into a Medieval ruler and his army could certainly have profound effects. Without any concern for divine judgment, they would be unrestrained by Medieval courtesies and customs and could pursue strategic aims more efficiently (however, you might consider what the general population might think of this ruler and his army? If the people kept their religious sensibilities this ruler would certainly be seen as a crazed, illegitimate tyrant, perhaps even an antichrist).

As a final point I would note that not all pre-modern warfare is characterized by religious inspired restraint. For example, in the campaigns of Alexander the Great, we see a classic example of a king who does deliberately seek decisive battle to invade his rival and overthrow them. Therefore it would be perfectly plausible for the ruler in your story to find his inspiration from the past rather then the future.

Answer 11

I'm not really sure what you mean by modern warfare theory. I'm going to make the assumption that you're talking about logistics, and possibly wargaming scenarios.

Logistics could be interesting. Generally, at least in European Warfare, as a soldier you provided your equipment and scavenged off the land(cheating a little with the link here - https://en.wikipedia.org/wiki/Medieval_warfare#Supplies_and_logistics). Having a standard set of interchangeable equipment and supply trains would give you an advantage over someone who didn't have that, especially over an extended campaign.

Wargaming or looking at the overall strategy of a military campaign has been used on and off throughout history (https://en.wikipedia.org/wiki/Military_strategy). Generally, if you're doing it, you have an advantage over those who aren't (see the Greek/Persian example in the link).

To be honest, I think if you want to make a massive difference in warfare, a fast effective method of communication would be most effective.

Answer 12

To take a full profit from our modern warfare knowledge, Gary would need:

• knowledge of the warfare theories (Sun Tzu and Clausewitz, for example),
• knowledge of past battles and used tactics (review of what was done, why, and what was the outcome would be profitable),
• knowledge of the technology/tactics and troops available to him (nice and great to know about aerial coverage, but well, not going to be too useful for him),
• capacity to adapt to his environment (which requires the knowledge mentioned earlier).

And now, assuming he has all the preceding points, here are a couple of things he could/should be doing...

... as a Lord

The first thing it to make sure that the war/battle is the best alternative. The army is a tool for politics. But not the only one. He should define precisely the goals he wants to achieve, and evaluate the various means to achieve it. It the war is the best option, the scope and objective should be clearly defined (see the USA in Irak, Sun-Tzu, Clausewitz).

The second thing is that no one can wage a war without money. So he needs to boost his economy, increase his surplus, find financial support, etc. Once this has been achieved the war can be considered (e.g. Charles VII in the 100-years war).

The third element is to make sure that he has a solid weapon industry or supply. He needs to arm his troops.

For longer-term, he needs to make sure that he stays on top of things. So universities and schools, might be able to help with innovative strategies/tactics/weapons.

Another point of importance, is that he is well read with Macchiavel. He knows how to rule his own Lordship as well as dominions he might get in possession of.

... as the Army's Chief-General

The Army is a tool that should be ready for the politics. They should prepare to various possibilities, but only act upon the decision of the politics.

As Sun Tzu teaches us, the first thing is to know you enemy. The Chief-General should organise spies networks in order to gather a good information on the armies of any potential adversaries.

Then, modern and current armies rely essentially on well-trained professional troops. He needs to recruit and train people. Note that one possible advantage of really modern knowledge: women can fight equally well, they could increase the size of the army. But that might be some cultural shock. But maintaining a professional army during peace is extremely expensive, so he needs to find methods to do it. Like regular short trainings (see Swiss' military service).

He also needs to invests considerably in logistics. Food, money and anmunitions should flow without issue during a campaign. As mentioned in other answers, hygiene is also a crucial element.

Then military engineering might play a crucial role. He should ensure to have a supply of engineers who could provide technical solutions (crossing a river, take a castle, etc.).

Even if he takes on the three posts described here, he can't be everywhere, every time. Furthermore, recent strategies used fake movement and armies to mask the real intentions (see Operation Fortitude). So he needs to have a set of trusted, capable generals to carry-out the order and be ready to adapt to the situation. This can be done by knowing the people, and promote worthy ones to posts with responsibilities, regardless of their origin (note that this may not be so well accepted for a brutal change). But this also needs to have training... and trainers. Which would rely on the universities and schools developed as mentioned.

... as a Field General

Here, the knowledge of the past battles would be very important.

Scouts are important to know the preparation of the enemies as well as recognise the terrain.

He knows to separate the strategy from the tactics. A battle may be lost, if it gives an advantage for the campaign.

Find the best field. Always go to battle when the field favour his army. Or at least does not go against him. Terrain knowledge from the scout is crucial.

Use a combination of the various arms available. Typically light and heavy cavalries, peakesmen, archery for European's MA. Use smaller specialised units and deploy them to counter the opponents tactics. Keep reserve troops.

Two very important lessons to take: mobility. Even the best troops (hoplites) could be out-maneuvered. He should make sure that his troops are reactive and can be quick to move. And communication: the orders and reports should rely on well trained troops and officers, as well as well established communication channels. The next tactical move should be communicated effectively to the soldiers.

As he prepared his own troops to be well supplied, mobile and well informed, he knows the crucial importance of those. He may then attempt to disrupt his enemies' supply or communication lines.

Conclusion

Assuming that apart from the knowledge, he has the required capacities, he might greatly profit from that obtained knowledge in his military actions. However, many/some of those need time to be effective. In our history, some of those elements took really centuries to get some effective value.

Answer 13

Gustavus Adolphus brought the concept of COMBINED ARMS to the old world. Same weapons as everybody else, but a different way to organize and train and fight that made combat more effective at the unit level.

Also, sci-fi author H. Beam Piper liked using real battles in his time-travel (heh) stories. He is worth a look.

Answer 14

I am no expert but here are a few things I think modern warfare knowledge might bring:

1) A destruction of arbitrary classes

Training, armor, and weapons were often distributed based on societal status. This lead to horribly trained foot-soldiers with insufficient weapons. As others have pointed out, this also resulted in very useful tools like crossbows being disdained. Finally, modern warfare values troop cohesion which is damaged by having arbitrary class structures.

2) Guerrilla Tactics

Though more common than many people believe, Guerrilla tactics were not extensively employed. A modern commander would have far less sympathies for "propriety" and "honor" on the battlefield, thus allowing more underhanded techniques to tip the battle. On the other hand, a modern commander would be appalled at some of the "barbery" he witnessed, so this could be a double-edged sword.

3) Understanding of Modern Psychological Warfare

This would be valuable for preventing troop morale breakdown, and would also give the Lord the ability to strike blows to the enemy that would be highly demoralizing but not immediately of prestige or other tactical value. These type of attacks would be very alien to many of his opponents.

4) Supply chain and Engineering Corp.

The Romans were very aware of the value of engineering corps, but this knowledge seemed to have been lost in much of the Middle Ages. This was at least partially due to problems listed in the first item in this list. A proper engineering corp would provide the troops with proper supply routes, more rapid movement, and better and more defensible quarters.

Answer 15

The book On Killing: The Psychological Cost of Learning to Kill in War and Society - and this video - reports that:

1. 90% of rifles found dropped at the Battle of Gettysburg were loaded.
2. This and other evidence indicates an innate human resistance to killing, manifesting in not shooting when they have the chance, or not aiming when they shoot.
3. Modern armies have developed Pavlovian and operant conditioning - such as replacing bullseye targets with silhouette targets - to increase firing rates.

Obviously, if only 10% of your guys are shooting to kill and you can get that up to 20%, it's almost the same as having twice as many guys - except you don't need twice as much food and wages.

You could extend this to your fictional world, and claim that with with modern training techniques and understanding of human nature you could make a force of the same size much more effective.

Of course, you could argue the not-killing evidence doesn't extend to medieval battles; people's instincts might be different when the threat is right in their face.

Answer 16

strategy is based on available resources, so almost nothing from modern warfare could be implemented. Camouflage painting maybe. But historical knowledge of military expert could give to Gary things like:
- advanced fortification, both field and long-term
- something like spanish tertia (offtopic - I tried to recreate it in M&B PoP, if ya know what I mean ;-) and it kinda works good)
- chain of command, military ranks
- advanced siege and field mechanical artillery, due to math and other knowledge

Answer 17

Modern warfare requires modern weapons/tools. So... many tactics, formations and most rules do not apply because neither enemy nor they themselves do have the tools to make them useful.

What would come in handy would be the modern training methods, ranking system, execution of commands/discipline and how supply chains are set up. Also, many 'modern' ideas, like hygiene and that a̶l̶c̶o̶h̶o̶l̶ ̶s̶h̶o̶u̶l̶d̶ ̶n̶o̶t̶ ̶b̶e̶ ̶a̶ ̶r̶e̶p̶l̶a̶c̶e̶m̶e̶n̶t̶ ̶o̶f̶ ̶w̶a̶t̶e̶r alcohol should be consumed as little as possible. Also clearing up myths about mystical herbs and ground-up animal parts that at best do no harm.

With modern methods, you would be held back by those times limitations and problems. Key would be the knowledge to either overcome those limitations, with essentially the same methods that were used in our history or to compromise with what was available.

Raising a professional army would already be quite a benefit, apply what we now know about health and training and it would be quite the formidable army too. Battle in these times usually took place at the battlefield, literally. Two opposing armies would meet at a specific area and fight to the last man standing.

Using what would be considered underhanded methods Gary could probably overthrow many kingdoms with guerilla warfare, spies/infiltration, assassination and less effective versions of the Blitzkrieg tactic (conquering as fast as possible, really effective if you have machines to get around, tanks etc). Also preparing the country for war. Setting up supply lines, shelters for wounded soldiers etc. using propaganda to get the population riled up and change their mindset to pro-war. Also training most soldiers of the professional army to lead untrained people. If it were required stocking up on manpower by drafting from the general population would work quite well too.