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.

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    $\begingroup$ iam not sure modern formation or tactic can work except guerilla warfare since modern warfare is smaller or in unit form while in medieval it was big formation kind even if they just equip the equivalent of gun like crossbow iam not sure they can farewell against cavalry charge or enemy shield wall. $\endgroup$ – Li Jun Oct 1 at 10:19
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    $\begingroup$ or are your medieval setting already develop some basic gunpowder? $\endgroup$ – Li Jun Oct 1 at 10:22
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    $\begingroup$ @LiJun Maybe there are some very basic gun powder weapons or canons in this setting, but they're way too expensive to be used on a large scale $\endgroup$ – Guillaume C. Oct 1 at 10:24
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    $\begingroup$ Even what we consider modern concepts like 4GW, "Hybrid Warfare" or "Unrestricted Warfare" had analogues that were appropriate for the time. A chevauchée was an attack on the local economy, put the local lord's reputation at risk if he could not deal with it and could destabilize entire regions if other lords began fighting over the land. Heralds bringing songs and stories was a form of PSYOPS. Warfare is about effects, logistics and tactics is just how you achieve them with your tools at hand. $\endgroup$ – Thucydides Oct 1 at 16:18
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    $\begingroup$ Modern tactics reflect modern weapons and armour. It doesn't work with medieval weapons and armour. The tactics of the time are the correct tactics for the technology. If you change weapons, the tactics will change to suit them. $\endgroup$ – Thorne Oct 2 at 1:20

17 Answers 17


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.

  • $\begingroup$ Comments are not for extended discussion; this conversation has been moved to chat. $\endgroup$ – Monty Wild Oct 5 at 11:39

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.

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    $\begingroup$ I didn't expect an history session, but that was quite interesting. Thank you! I wish I could upvote you. $\endgroup$ – Guillaume C. Oct 1 at 10:54
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    $\begingroup$ Yes, +1 for the history lesson, and our regularly scheduled reminder that improving history via timetravel is hella hard. (and also that "guns, germs and steel" needs to be backed up with "farming, medicine and midwifery" if you're serious about taking over the world) $\endgroup$ – Starfish Prime Oct 1 at 10:57
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    $\begingroup$ @Upper_Case: The point is that there was no "army" in the sense that we understand it. When a ruler decided or needed to wage war they summoned their vassals with their men. This heterogeneous assemblage of men formed the army, which existed for a very limited span of time, and then everybody went back to their business. He does not have "plenty of time and gold to modify his army". Not in western Europe during the Middle Ages. Elsewhere, possibly. Very late European Middle Ages, just maybe. In the Renaissance, more likely. In the Early Modern period, certainly. $\endgroup$ – AlexP Oct 1 at 20:51
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    $\begingroup$ @Upper_Case: What I'm saying is that medieval commanders had good theoretical training. (Well, some of them, at least.) They were not barbarians. (Well, some of them were barbarians, but we are not speaking of barbarians here.) What they didn't have was the scope of applying the theoretical knowledge. At the battle of Hastings each side fielded forces about the size of one Roman legion, and even those small forces were ephemeral assemblages. Later military theory emphasized training, maneuver, logistics etc. which were simply out of reach for medieval commanders. $\endgroup$ – AlexP Oct 1 at 21:42
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    $\begingroup$ @Upper_Case: When all you have is a few hundred men under your direct command, plus maybe one or two thousand men-at-arms under the command of your vassals (which most of the time rule their own fiefs autonomously) plus a few thousand militia, there isn't much you can do in terms of complex battle plans: those people never trained together. And when the general economic base is medieval you simply cannot create a dependable supply chain; logistics means "get as much non-perishable food at the place where the army is gathering" and little else. $\endgroup$ – AlexP Oct 1 at 21:46

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.

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    $\begingroup$ This seems to be the only practically usable answer. If you can't give them hardware or technology, then medical knowledge is the only kind of knowledge you could provide them. Tactics like what formation to stand in, how to move on the battlefield, what weapons to use and so on would be useless, as the medieval knights knew their own equipment (and how to use it) much better, due to experience, than any modern advisor. $\endgroup$ – vsz Oct 2 at 6:16
  • $\begingroup$ Definitely this. Most modern warfare theory relies on technology like vehicles, artillery, aircraft, and people with automatic firearms who have more firepower than a large group of people from earlier centuries. Modern squad-based tactics are all based around infantry with access to significant firepower, which was not the case in earlier centuries, particularly those with very primitive or no firearms at all. $\endgroup$ – Kevin Peter Oct 4 at 17:55

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.

  • $\begingroup$ Thank you for your reply. Those are excellent points, and you're right that Gary's way to use of such an information depends on his end's goal. While I want Gary to be as general (pun not intended) as possible, my version of Gary is more a commander than a schemer. :) $\endgroup$ – Guillaume C. Oct 1 at 12:34
  • $\begingroup$ With a staff trained in the proper principles to handle the information flow and detailed planning, Lord Gary can use nimble combined-arms forces, combined with best use of terrain, to find ways to minimize enemy strengths, to ambush and trap larger forces, and to use a wider array of tools to frustrate the enemy leadership. $\endgroup$ – user535733 Oct 1 at 13:29
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    $\begingroup$ Don't forget Sun Tzu, The Art of War. Although it pre-dates, by many centuries, Europe getting to Gary's presumed level of technology, it is still used as a strategy textbook. It may help Gary learn to be a schemer. For asymmetrical warfare, regardless of which side Gary is on, I would add Mao Zedong "On Protracted War". $\endgroup$ – Patricia Shanahan Oct 1 at 13:53
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    $\begingroup$ @PatriciaShanahan - If the question were "whose works should he study?" then Sun Tzu is indeed a good starting point. However, the question specifically asks for modern theory, which it is not. So I did not include it. Honestly, folks who read Jomini are getting a lot of updated Sun Tzu in there. $\endgroup$ – user535733 Oct 1 at 15:17
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    $\begingroup$ @PatriciaShanahan perhaps we disagree on relevant vs. modern. I'm sure not denigrating Sun Tzu -- it's an easy read, it's a great introduction to a lot of concepts, it's an important work, it's hugely influential, and it's definitely still relevant...but it's not modern. Many of the officers of NATO do read Sun Tzu (it's relevant)...but ALL of them spend much more of their careers learning, parsing, analyzing, and implementing the products of Jomini and Von Clausewitz (modern). A poor analogy: My biology texts didn't include Darwin, but included a stack that built upon his great work $\endgroup$ – user535733 Oct 1 at 16:20

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.

  • $\begingroup$ Thank you, would special forces fall within the asymmetrical concepts you're thinking about? $\endgroup$ – Guillaume C. Oct 1 at 10:37
  • $\begingroup$ @GuillaumeC., based on the information I have added, no. $\endgroup$ – L.Dutch - Reinstate Monica Oct 1 at 10:49
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    $\begingroup$ Communication: Actually, introducing long distance communication is a real deal-breaker. The use of semaphores is an excellent example of really low-tech solutions making a difference. $\endgroup$ – RedSonja Oct 2 at 8:08
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    $\begingroup$ @RedSonja, actually drums, flags, trumpets were used also as a way of using codified long distance communication $\endgroup$ – L.Dutch - Reinstate Monica Oct 2 at 9:34
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    $\begingroup$ @Falco, technology to build at least a practical postal service was certainly there, so it seems more like organizational issue. Case in the point: when the semaphore telegraphs were built, most were still reserved for government use even though opening them for commercial traffic would have significantly helped economy (and probably covered the costs); so it seems the governments were not really thinking about trade that much even well into modern times, and if somebody did, they could move things forward quite a bit. $\endgroup$ – Jan Hudec Oct 2 at 21:05

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.
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    $\begingroup$ Pike formations require training. They require a lot of training. You need to practice marching in close formation to get the density of pikes needed, and to build up the unit cohesion that will let your pike square stand firm in the face of a thundering cavalry charge. If you just give pikes to your untrained peasant levy, that levy will take up a loose formation to keep from tripping over each other's pikes, and will scatter at the first sign of opposition. (At a rough estimate, based on Renaissance-era formations, training a pike square takes a full campaign season.) $\endgroup$ – Mark Oct 2 at 21:13
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    $\begingroup$ @Mark You don't need that much training to deploy a basic static schiltron. Yes, for more complicated formations more experience is required, but you enemy doesn't have it either. It won't win your battles alone, as a professional tercio could, but it is still a significant force multiplier nonetheless, and may just be enough to tip the balance in your favour. Another example would be Battle of Legnano, where a spear formation was improvised and not trained beforehand, yet effective enough to hold off Imperial army for hours. $\endgroup$ – Alice Oct 2 at 22:24
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    $\begingroup$ @Mark, I picked up basic pike formations in two day's training when I started doing English Civil war re-enactment. And I'm a keyboard monkey with no stamina or coordination. OK, so standing firm in the face of cavalry charge is hard, even when you know they're NOT trying to kill you, but the point remains. $\endgroup$ – Chris the Hairy One Oct 3 at 14:28

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.

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    $\begingroup$ As Edward III might have said, "If you want to train a longbowman, start with his grandfather." $\endgroup$ – Starfish Prime Oct 1 at 11:28
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    $\begingroup$ The problem with things like extensive drilling of the troops is that medieval Europe doesn't have an economy that can support a non-trivial standing army. If you want to wage war, you've got a few months of summer to do it in, before the bulk of your troops need to go home and harvest the crops. $\endgroup$ – Mark Oct 1 at 20:24
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    $\begingroup$ Medieval warlords were not morons. People today tend to believe they are smarter in every topic, but in case of medieval warfare the medieval lords had much more experience in the effectiveness of their own weapons and their own troops than any modern advisor. Agincourt wasn't an example of longbowmen being inherently superior, the French lost due to muddy terrain and some tactical blunders. $\endgroup$ – vsz Oct 2 at 6:11
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    $\begingroup$ @mark well Gary lives in a "Europe-ish" world/continent. Thus we don't know for certain what sort of things Gary might be able to pull off in OP's fantasy setting. The Warcraft universe is medieval (often) "Europe-ish" and they have war all the time. So it's a matter of the world's creator I would say. Also at vsz, I never said medieval people were morons, they were smarter in a lot of ways than us today (and in some aspects lesser so). I'm simply saying that Gary would have a lot of knowledge he could experiment with. $\endgroup$ – Finn Oct 2 at 6:30

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.

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    $\begingroup$ And an awful lot of food produced wasted away because it wasn't preserved properly. Introduce low-tech methods like drying, salting, silage, etc, and ensure they are used by everybody. Centralise storage of grain - see Ancient Egypt. Merciless rodent control. $\endgroup$ – RedSonja Oct 2 at 8:12
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    $\begingroup$ @RedSonja, drying was known. Smoking was known. Salting was known. They were also either expensive, labor-intensive, or both. And the big source of loss wasn't to bacterial spoilage, but to consumption by vermin, which is also expensive and/or labor-intensive to deal with. $\endgroup$ – Mark Oct 2 at 21:01
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    $\begingroup$ @Mark, reinstating cats to their rightful demigod status would help a lot ;-). $\endgroup$ – Jan Hudec Oct 2 at 21:13

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.

  • $\begingroup$ Yes, I like examining the progression of Roman Military as an example because of the historical transition from levy to professional soldiers, the centralised command structure, campaign logistics and adaptive combat tactics eg. auxiliary troops and battle rotation. $\endgroup$ – vinchenso Oct 2 at 10:55
  • $\begingroup$ If you really want something more modern, maybe take inspiration from Frederick the Great's tactical battle maneuvers or Napolean's grand strategy in Operational Mobility. Both of them ultimately focus on force concentration and routing the enemy from the field of battle. $\endgroup$ – vinchenso Oct 2 at 11:04
  • $\begingroup$ *semaphores(or *sophomores?) $\endgroup$ – user28434 Oct 8 at 12:04

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.


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.


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.


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.


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.

  • $\begingroup$ Welcome to the Wroldbuilding Stack Exchange! For a first answer, yours is rather good. I would like to encourage you to improve your answer by adding more sources, quotes and examples and linking to other articles on the web. It usually doesn't take much work, but greatly improves the quality of the answer. $\endgroup$ – A Lambent Eye Oct 3 at 12:08

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.

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    $\begingroup$ Destruction of arbitrary classes is going to generate a revolt or two. A better option is to work within the class system, by providing standard equipment to each group (eg. a standard spear, helmet, and leather jerkin to the peasant levy). Guerrilla tactics aren't much different from banditry, which medieval lords have plenty of experience dealing with. Psychological warfare was well-understood, if not formalized the way it is today. And there were professional engineers -- there just weren't very many, because combat engineering is expensive. $\endgroup$ – Mark Oct 2 at 21:27
  • $\begingroup$ The original question clearly states: "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..." Therefore my answer is perfectly within the bounds of the question. Had he not stated this, then I would agree that many of these changes would be impractical because his men would not accept them, at least not quickly. I would say "banditry" is nothing like organized guerrilla warfare on the scale of something like the CIA would train and use. Nor was there a field of psychology. $\endgroup$ – shellster Oct 2 at 23:22

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.

  • $\begingroup$ Winning in combat is not about killing the other person, it's about being able to make that other person do what you want (Sun Tzu has a well-known quote to this effect, and most other military writers express the same sentiment). Increasing the willingness of your troops to kill is far from the most effective way to increase your combat capabilities. $\endgroup$ – Mark Oct 3 at 21:40

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

  • $\begingroup$ Welcome to the Worldbuilding Stack Exchange and thank you for your valuable contribution! I would like to suggest you improve your answer further by adding sources, quotes and examples and improving readability (i.e. capitalisation). $\endgroup$ – A Lambent Eye Oct 4 at 7:54

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.

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    $\begingroup$ Alcohol is a reasonable replacement for water if all the available water is filled with disease, which was quite common back then (and often recurs even now during times of crisis). Small beer is preferable to cholera, and bulk sterilisation of water with medieval technology is likely to be quite space, time and fuel intensive on the scale of an army. $\endgroup$ – Starfish Prime Oct 1 at 11:48
  • $\begingroup$ completely agree with starfish's point, ale was often considered much safer to drink than water as there was no filtration or sterilization techniques known during this period. A river such as the Thames in London was famously unsanitary $\endgroup$ – BKlassen Oct 1 at 15:37
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    $\begingroup$ There's so much wrong with this that I don't know where to start. Literally the only thing that's indisputably correct is the first paragraph; most of the rest of it ignores the social, economic, and military realities of the time. $\endgroup$ – Mark Oct 1 at 20:30

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