Would modern age military skills be useful during the crusades?

Question

Modern era western company, with plenty of combat experience in Iraq & Afghanistan, is magically transported from East Syria into the newly founded kingdom of Jerusalem, right after the first crusade. Their clothes, weapons & equipment are replaced with age appropriate items, such as swords, spears, horses & chain mail. Left with only 300 knights and 2000 foot soldiers, Godfrey of Bouillon promptly admits the newcomers into his army.

Would modern era skills & tactics would be of any use in fighting the Seljuks, Saracens & Byzantines?

No modern age technology is available nor it could be introduced.

Language barrier is handwaved.

Modern troops don't have experience in medieval weaponry, with few exceptions. A few could ride horses, as they come from farm families who owned horses. A few could use bows, as they have hunting experience. And a few could use swords, due to exposure to certain martial arts. The rest will have to learn.

My story tends toward comedic effects, something like The Visitors in reverse.

Answer 1

Back in the good old days we would fight with melee weapons like swords, etc. So, in a bunch of special forces, snipers would probably be useless: rifle-training doesn't translate to swordsmanship. That being said, swords and spears are relatively easy to learn (if used as hack-and-slash or point-and-stab weapons respectively). But, military training of today is not entirely useless.

1. Discipline: Soldiers of all time-periods were trained for discipline. Your fancy swordsmanship will be useless if you run away from loud noises. Similarly, since our militaries are trained to handle extreme dins of battle, although a medieval war would be different for them, it would be a relatively quiet affair compared to the machine-gun fire that our troops are used to.
2. Survival skills: Looking for cover will arguably be easier for modern troops as they are very extensively trained in hiding from enemy units. Arrows and other ranged weapons are comparatively easy to hide from. Which leads me to my next point.
3. Urban warfare: If war leads to populated regions like cities and towns, I'd argue that our soldiers are more prepared for the nature of combat in cities. Most soldiers are trained for open war in an open battlefield, but I'd say our future-age soldiers would do better in these conditions than the typical soldier.
4. Superior training: This relates to all my points. Every soldier nowadays receives not only gun-training but also hand-to-hand combat training. This means that our troops are likely to be deadly even when disarmed. Hell, we've had centuries to improve on knife-fighting skills. Also, our boys are kind of ripped. Stuff like medieval farming does toughen up the body, but our soldiers are toughened up specifically for the nature of war.

In conclusion, I'd argue that even though modern soldiers would have no idea how to handle themselves in societies of the past, they would be killing machines compared to the average soldier. Now, versus knights and more specialized troops, not so much without the appropriate armour, but they'd definitely put up a fight. Maybe I'm a little too patriotic for our present-day soldiers, but I'd favor their chances in the line of combat.

Logistics: I heard this word mentioned a whole lot in the comments for this question. If anyone in the army has a BA in management, it might help the armies of yore to figure out how to manage their resources more effectively.

Yes, horseback riding is important, but the vast portion of any army in the good old days was composed of foot soldiers. With the discipline of modern troops, they would be exceptional trainers for Saladin's armies (or his enemy's armies).

And because most modern soldiers know how to read maps (and more importantly, read in general), this could help them transfer information to each other in a more clandestine manner than was available in those times. Plus, learning to ride a horse isn't hard - being an expert is. Don't expect to be able to out-ride a Mongol, but expect them to know how to cause some damage.

Of course, I say this all assuming that our modern soldiers don't accidentally kill everyone in the past with the diseases that we are immune to. I hope this helps - I'm open to criticism.

Answer 2

No

Modern soldiers are trained and equipped to modern warfare. They are next to useless for ancient warfare. At best, they wouldn't be better than any other piece-of-flesh to make for cannon-fodder and more probably than not they would be a dead weight to get rid off at the first opportunity.

Even handwaving the language problems that would render them completely useless, no knowledge they could gather with them is going to be useful or directly applicable. I think most answers in this post are overly optimistic, minimizing or ignoring the hurdles any modern person would have surviving in a harsh war campaign such as the Crusades were. Also, it seems that we are overestimating the value of knowledge of basic theory without realizing the vast, often impassable distance between theory and practice, and specially how much of these knowledge and technology relies on layers and layers of other knowledge and technologies which wouldn't be disposable. Summarizing some of the supposed advantages of our modern soldiers in alphabetical order:

• Digging latrines: was known by the Assyrian army, some 2,000 years before the Crusades. Every army that has existed has dug latrines when camping, if only because they didn't want to smell shit while eating.
• Discipline: they'll find theirs is not superior to that of the rest of the army. Particularly, being trapped deep inside enemy territory does wonders to prevent desertions.
• Encryption: cyphers had been used in warfare for at least as long as warfare was conducted by more than one attacking unit at a time. Crusaders knew encryption and used cyphered communications if necessary. Sure, our methods are harder to break, but since the ones they were using were also probably unbreakable by the enemy, it doesn't add any security, only longer cypher times.
• Field sanitation and hygiene: same as logistics. One thing is to know and another one is to apply. So you know medicine? Ok, but what do you do without antibiotics, sterilized equipment, clean tools...? You do what you can, in less than ideal conditions. Just like their doctors did. If you read Noah Gordon's "The Physician" you'll see that most first-aid and wound treatments were already known back then. 99% of modern medicine won't be available to the modern doctors, nor easily produced by then on the field. But they will know for sure the wounded are going to die.
• Logistics: modern soldiers may know everything that can be known about logistics. It won't improve Godfrey of Buillon's resources in the least. What good is to know how many lorries would it take to transport two armored divisions from Haifa to Bagdad if it's not going to increase the amount of camels and donkeys that you have? You don't have to go back in time to the Crusades, just send your soldiers to Ethiopia and make them work with the Ethiopian budget of defense and see what they can achieve with that. Without the unlimited funds and resources of the US Army, logistics knowledge is worthless. Logistics wins wars, no doubt about it. Having logistics wins wars, that is, not knowing about logistics. You can reasonably assume that the Crusaders' leaders managed their logistics the best that could be done in those times.
• Psyops: the crusaders have very limited to no method to reach the enemy's population, so hardly they could try anything like that. The only psyop known at those times was initiating a siege. Then the population besieged could be targeted for psyops.
• Reading maps: maps weren't invented yesterday. The crusaders also knew how to read them. They can't improve their quality or precision, so they don't add anything to what the crusaders already had.
• Superior training: not really. Surely modern soldiers are better at boxing or judo, even they may know something about knife fighting in a nightclub, but fighting a lightly armored opponent with a scimitar, no, they really don't know shit about it.
• Survival skills: will cost them their lives. In modern warfare, under enemy fire you look for cover. In ancient times if you break the line because the enemy is shooting arrows at you you are hanged for cowardice. "Survival skills" at those times meant putting a stiff upper lip and praying the arrow hits your shield (or your comrades).
• Urban warfare: there wasn't any. Whenever an army entered a city the battle was over. What came then was pillage and rape, but there's absolutely no need for urban warfare knowlegde. Nobody will be waiting at home with an AK-47 and two Molotov cocktails.

And so on. All of this summarizes why modern soldiers wouldn't be any better than ancient soldiers. Now for a few reasons on why they would be probably much worse:

• Overgrown: our modern soldiers are used to a 1,500 to 2,500 kcal/day diet. Crusaders will do with a little less than 1,000, which will render our modern soldiers weak, dehydrated, tired and utterly demoralized in a few days. An army marches on his stomach, Napoleon said, but their stomachs are too big for the frugal necessities of the day.
• Sluggish: it's beautiful to know much about hygiene, but what do you do without water purification pills? Boiling water is out of the question: not enough boilers, not enough fuel, not enough time. By the time you have boilt water for the whole camp a day has passed and you have to start boiling water again. You are stuck. You don't have any options but drink and pray, and our chlorinated-water-used stomachs won't resist as much as the tougher drink-or-die naturals of the time. Same thing for food in a time with no cans, no vacuum bags, no freezers and no pasteurization at all.

Answer 3

Medicine

In addition to the other answers, I would like add basic first aid and medicine.

The lowest modern field medic could revolutionize a field hospital of that age... if they can get people to listen to them.

I am not a medic, so you might want to consult other sources of information, but off the top of my head I can think of:

• The very idea of first aid. Every soldier is drilled in the most basic things, most notably how to stop a bleeding. Every soldier is carrying a small clean bandage.

• Keep clean. Keep the wounds clean. Keep the surgeons hands and tools clean. Use clean bandages.

• Boiling water. Before drinking, but also as a way to clean things. Clean!

• Stop bleeding the patients! They have already lost enough blood!

• Pressure dressings? The proper way to apply a bandage to stop bleeding. Not sure what the crusaders already knew about this.

I am sure there is more, but my knowledge is limited. Both about modern and ancient field medicine.

Answer 4

The key advantages the modern soldiers would have would not be direct combat skills, but rather the skills of logistics, support and enabling. The historical knowledge could also be useful for the Crusader kingdoms, allowing them to identify key personalities and linkages.

The key to any military operation is logistics, and the Crusader kingdoms had multiple challenges. They were at the end of a long supply line to Europe, and were in an alien environment which was not economically developed in the ways that the Crusaders were familiar with. Trying to wrest a living would be very challenging, and the sort of extractive economies that the European nobility was used to would not be viable. Knowledge of logistics would allow the Crusaders to operate more efficiently.

Supporters and enablers would include such skills like map making, psychological operations (PSYOPS), communications, cryptology (codes) and battlefield medicine. Field sanitation and hygiene would also do a lot to reduce wastage of the Crusader manpower.

So by becoming the staff of the Crusader kingdom and applying the modern skills to support the Crusader logistics and operations, the Crusaders will be more effective when conducting operations in general. If the newcomers have enough historical knowledge (and soldiers are often history geeks), then the Crusader armies could focus their operations against key personnel or groups. So the modern company may not be able to directly affect the battles, but they could leverage their knowledge to make the Crusaders more effective, and possibly allow the Latin Kingdoms in the Middle East to have survived for far longer than they did.

Answer 5

Digging latrines

(and knowing it needs to be done.)

I'm sure modern soldiers probably have toilet blocks on trailers running to any long term encampment, so you might need to go back a few decades to get soldiers with real shitpit digging skills, but the single greatest thing you could bring to a medieval encampment is a long drop.

Answer 6

I wouldn't use them as soldiers, they're not trained for what a battle was like back then.

Rather, they should be used as sniper-scouts. They are far more used to the use of stealth and they won't consider hiding to be cowardly. Sneak in, get information, get out, perhaps take out someone important with a crossbow or conduct acts of sabotage. (Think about the effect of harassment fire of flaming arrows against the enemy camp the night before a battle.)

Answer 7

Put them in the signal corps

The US Navy still uses the flag semaphore system, which can transmit arbitrary content at a rate of about eight words per minute(1). Unlike an Aldis lamp or electric telegraph, flag semaphore requires no technology (technically, not even the flags themselves), so any signalers would be able to begin immediately.

Compared to signalling methods at the time, which were slow and almost invariably only usable for pre-arranged messages(2), flag semaphore would be a big improvement.

These skills could be used to vastly enlarge the search area of any patrols. Any activity could be reported and described with more speed and accuracy. With relays, even long-distance, non-line-of-sight communication is possible.

Additionally, although modern methods of encryption might not be that useful, modern methods of cryptanalysis could be used to read intercepted messages, especially since most medieval ciphers were vulnerable to frequency analysis.

Answer 8

IMHO it strongly depends on exactly which kind of troops are "transported back".

Officers are trained also in warfare history and theory; this means they STUDIED all tactics devised through the centuries and they KNOW what was useful against a certain kind of enemies (including Seleucids, Saracins and related populations).

OTOH "cannon fodder" soldiers would be in hard difficulties without communication aids, binoculars etc... not to speak, of course, they would be hard pressed to march long distances without "proper boots" (wearing war sandals, as used at the time, takes hardened feet or you're going to get blisters all over); similar argument holds for arms and hands unused to sword and shield.

IF they are given time to adjust (mainly strengthen their limbs and skin) they would have a fighting chance, otherwise they could be useful as trainers and advisors.

Answer 9

As a body of fighting men (I am handwaving an all-male force because things are hard enough without convincing Crusaders that a woman could be a soldier and should be listened to) they're not worth much. Their training is all wrong, and might even be counterproductive. For example if you're not a sniper you're not usually seeing the look on a man's face when you kill him. "Aimed fire" isn't as much a thing as "suppression and hey that'll likely kill the enemy to boot". Killing a man face-to-face is what matters in the Middle Ages, and our heroes have been brought up to value individual life and only LATER taught to kill. That's a fundamentally different thing than assuming anyone who's lived past 20 has won the lottery and being taught to swing a sword at a living being since you were old enough to hold one.

If you decide you've got a band of cold-blooded combat junkies who won't balk at close-in work, you might have an interesting fighting force depending on how they're equipped. As someone already mentioned they'll be huge compared to the average soldier, and with a few weeks of drill could make for decent line infantry. Mind you, decent, not great. Even with combatives training all barring the odd ARMA-nerd (Ancient and Renaissance Martial Arts) will be utterly incompetent with medieval weapons. Give them good armor, which given the loads they carry in modern battle shouldn't slow them too much, and they'll be able to work through levy-equivalents. But they'd last about 5 minutes against trained-for-decades knights and Sarassin equivalents. To think otherwise would be like thinking I could train Shaolin Monks in modern weapons for a few weeks and have them beat US Infantry in a gunfight. It just doesn't work that way.

However from a storytelling perspective they likely have one VERY important card to play. They know how it ends. Some 2LT or nerdy infantryman at the very least can go to the company commander (who if they were to have any effect at all must be a guy that Godfrey believes) and tell him that the Crusades won't ever draw enough Europeans to win the Holy Land for all time. Maybe they tell him details like "you'll die of some disease if you go to Caesarea" maybe they say "hey our records said the Muslims had an army of XXXX at this date" If Godfrey believes they're from the future he may well take whatever they tell him as a sign from God. But as a purely fighting force they're just another hundred-odd bodies in the line.

Answer 10

The advantage would be huge, because modern armies don't operate on the "meat shield / cannon fodder" paradigm.

It's all about force multiplication. Consider all the force multipliers at play:

• They will insist on hygenic conditions for their camp at least, and other commanders are going to notice. "Why do you boil your drinking water?" "Why are you so fussy about where you pee and poop?" "Why are your medics so interested in alcohol?" "How come you have so few sick soldiers?"
• Their medics would be first-rate, and use all their modern knowledge to keep people healthy and do field medicine to the extent practicable. Just look at Outlander for examples of that, where they react to Claire like "you do what with what!!??" and that's in the mid-17th century; you're in the 11th.
  • Before someone says "Medieval medics weren't stupid", beg pardon. Like Mark Twain is attributed to say, "what hurts you isn't what you don't know. It's what you know that just ain't so!" Medieval medicine is mired in that - so many taboos, axiomatic beliefs that were wrong, and Church edicts that couldn't be challenged.
  • Medics are the ultimate force multiplier. If Godfrey saw the results and took the medics' advice at face value, and propagated that training, it would greatly strengthen the army.
• Obviously the ancients were no slouches in logistics - a supply chain across the Mediterranean in 1050 is like a supply line to Mars today. But modern western armies are deeply committed to it. Again, if the logistical doctrine of the modern force can sway Godfrey, it would slow Godfrey down, but greatly stabilize the forces by solidifying the lines of communication.
• The modern doctrine of "Force Protection", would reject the idea of openly wasting assets in "chivalrous" square-on force-on-force confrontations. It would force command to avoid engagement except when they have an overwhelming advantage, and to set up those situations.
  • The army would become better at disengaging: avoiding or retreating from battle without much loss in strength, materiél or confidence.
  • The conscripts would notice that command is treating their lives as worth protecting and not to be wasted. That would greatly increase morale, improve their willingness to soldier and to train. Now even your conscripts are starting to look like a professional army.
• Command would be acting on better information. The moderns would bring a very different sense of command decisions and information gathering, so fewer moves would be made blindly or stupidly.
  • Disinformation would be a doctrine; moderns would be aware of tactics like Tecumseh's at Detroit, and would mislead enemy forces into fatal mistakes.
  • The moderns would be really, really, really good at scouting, since they are deeply trained in stealth tactics, and they have a good sense of what modern camouflage ought to look like. They aren't going to be caught out in a road; the enemy would never see them.
• They would also have a modern expectation of good signaling. And would improvise it in those times using light signals and Morse code. This could be done with a torch inside a helmet, for instance, aiming the light at another listening post, and interrupting it by stepping in front of it.

All in all, Godfrey's army would win the attrition war, suffering far fewer losses due to environment, even if the armies simply chased each other around the wilderness. When the army acted, it would do so more carefully, effectively and decisively.

Answer 11

IMHO few skills would be immediately usable:

• strategy: without any long distance observation and communication, most modern tactics and strategy will not be useable
• weapons proficiency: no firearms are accessible. The close combat skills would still be on topic, except that soldiers are trained to fight against knives, not heavy swords
• resistance and discipline: IMHO this would be the more immediately usable skills, but with little proficiency in available weapons, and tactics that would probably not be enough
• scouting: here again, modern soldiers specially in special forces are trained to hide which could be a nice point.

But modern knowledge could allow to rather quickly give a technological advantage: black powder is easy to produce with medieval technologies as are simple cannons. Dynamite does not require too complex base materials either.

IMHO the best use that could be made or modern troops would be to forget that they are soldiers but use their scientific and technological knowledge. The higher risk here would be that they could be burned for sorcery...

Answer 12

No.

Hand to hand or other close combat training in modern military is focused on 1:1 scenarios, and is not at all applicable to the experience of a footsoldier during the crusades.

Crucially, none of the modern troops have ever trained with a shield, and they certainly haven't trained in holding a shield wall (like, the most basic bread & butter tactic of the era). This means that they have no idea how to rotate the line. Assuming someone in the chain of command thought that far ahead, or was familiar with these sorts of minutiae, they might be smart enough to know that they will need to, but the soldiers have never drilled on this before and it's a somewhat complicated maneuver that you need to pull off while a bunch of people are trying to stab you.

The first time they attempted to rotate the front line of a wall they would absolutely fall apart. It'd be a complete and unmitigated disaster.

Assuming enough of them survive that experience to continue fighting, they will have no idea how to read signals communicated via banner, so they'll have no method of communicating with the larger army. These people are used to radio. They have no concept of how a medieval army communicates orders.

They are not used to co-ordinating maneuvers with units that are sized for the era. They are organized into squads, mostly, and all of their tactics assume much smaller organizational units then those fielded on a medieval battlefield. The command staff will need to re-organize the whole company and command structure to account for this, and unit cohesion will absolutely fall apart in the short term.

The life experience and prior training puts these individuals far above where most random recruits would start, but it is not a substitute for era specific training, and if they did not spent time preparing and learning from the peers, they would be worse than useless on the field.

Answer 13

Yes

Well,lets see a timeline of events for starters

As our modern company has been dropped right after 1 st crusade(about 1099 AD) and second crusade started at about 1147,I would say a lot depends upon what missions they had during this period.

• After the death of Godfrey of Bouillon,his brother Baldwin of
  Boulogne became the king of Jerusalem in 1100.
• In the year 1101 he laid siege to the city of Arsuf. Later,he also laid siege to the city of [Caesarea Maritima].3

Now,the thing to remember here is that both these sieges were short sieges of about 15 days mainly due to wide use of catapults and siege towers.

• He later goes on to capture many cities like Acre and Beirut.
• He tried to capture Tyre a few time but failed,which was only captured by Balwin II with the help of Venetian fleet.

During this period,Our modern company could be devastatingly effective.All the physiological and modern warfare,which other answers have said,would have been not so effective in H2H combat can be used in a siege.Furthermore,there is also chance for guerrilla warfare and urban warfare in such a scenario where a elite team can devastate a city under siege from within, by destroying food reserves and poisoning the water supply which were fair tactics during those periods.

The more bloodier battles also did take place but they were infrequent before the second crusade,Even these sieges had a gap of a year at least which would give our modern company enough and more time to survive,adapt and prepare a infrastructure to utilize those modern skills which would take time in that time period.

Furthermore,I would like to speculate that had such a company arrived in that period Baldwin I surely would have been able to capture Tyre thanks not only due to skills mentioned in above answers but also due to general ability to brainstorm ideas among themselves freely to devise some unorthodox plans based upon general prior knowledge about that historical period.

Answer 14

Behind-the-enemy-lines fight - new military should be better in hiding themself in crowds and strikes from back into most strategic place (like crossroads, water station) and gaining Big advantage with less effort due to better plannig and strategy.

Maps and possesion analysis - they will know what to look for in dangerous area and will not to go there unless proper reckon.

Trenches - ww1 style of digging fight that can be gamechanger if they are outnumbered and have to abandon strategic place. they just dig and wait for backup

Hybrid war and propaganda - using crowd tendencies to get the town without single shot. making the election (with right winner), get to the media, news, stories, whispers.

Better ways of gaining info - psychologic torture, fake drawning technique, profesional usage of agents to get info about opponents activities

And also - the good points from others.

Answer 15

I guess YES, they are a nice addition to that time.

As Akhil Sharma pointed out, those soldiers are dropped at a specific point in time. There is nearly one year preparation time until they have to be ready for the first siege, and another year until the siege really takes place. Yes, our people will be weaklings with weak feet needing toilet paper in the beginning. But they have a year preparation, maybe even more.

We can't quote Romans in any way - they were in some sciences much ahead of middle-aged Europe, even if they were using lots of bronze and leather instead of iron. But that knowledge was not transported far and much of it was forgotten in the pox chaos and church panic and Roman Reich breakdown that the Europeans had to endure. So let's just assume that the crusaders used standard tactics for their time, trained their weapons to perfection on their three-years-journey from Europe to the middle east, finished the first crusade, and when godefrey is already in his last year, our soldiers drop. And have no clue.

They will be bigger than the average European of the middle ages, roughly the size of well-nourished nobility people. Language is handwaved, so they might be able to convince somebody that their leader is some low ranked third born nobility guy, and thus being able to get an open ear in the leading ranks. This is the first difficulty someone from today will encounter - normal people were not listened to at all. Hopefully they have a captain or lieutenant who is good with words.

There, this guy, if he is good, can place some interesting messages. He can spread the knowledge of flag signaling, morse coding, Napoleon's concept of small hide-able movable units instead of big size armies, WW2 concept of the operational layer between tactic and strategy, sand filters for water, boiling of medical equipment, tactics that knights are not only run fast to the flank of a battle or support a weak spot (which has been done as standard) but maybe they can think of some tactics that allow knights to appear in several battles in short succession. This is all the communication, logistic, operation, hygiene stuff that has been said before in this thread.

But now, if this counts as not-allowed transfer of technology to former armies, there is still much good they can do. There are 50 years until the second crusade, and those people are not needed in the coming three sieges, and they know it! So, that's a strategic time scale, not a tactic time scale. We don't drop them into the middle of a sword fight, that'll be stupid. We could (they have one year time to train!) but we can make better use of them.

• Multiplication: founding of families and uprising of children in the name of the crusader culture until the second crusade comes. Each second surviving child can be an additional soldier for the battles to come. If the soldiers of our unit teach their family sand-filtering of water, basic (mouth)-hygiene, reading and writing, we'll have an army of healthy individuals.

• One of the reasons the crusades were failing was because culture eats strategy for breakfast. The crusaders had some military successes in the beginning but were then failing to root their culture into the people. So they needed continuing support from the homeland with an easy-to-disrupt 3000 km support chain. Imagine they had proper support at the front in the middle east, they could have done far better. If we plant 300 dedicated men in that culture and let each make 5-10 kids as was normal in these times, that's a lot of push on the cultural front.

• Canalisation/Water filtering and Garbage disposal: If those 300 families would push for both of these facilities in "their" city(ies) or village(s), they would be hardened against smallpox and cholera. Pox were depending on rats living in the garbage; cholera results from drinking water with microbes from other sick people. So it may be that just from these basic measures, they get a population which can "deliver" much more soldiers to the second crusade 50 years later, even when we cannot bring antibiotics.

• Again Canalisation, this time for the watering of plants. Along with the digging of wells, that's one of the biggies. You want more soldiers, you need to feed the people! Everyone who dies of hunger is one swordswinger less. Everyone who is fed by their new masters is a potential friend and not an enemy.

• Again, Garbage Disposal. Fertilize the crops! Don't know if it was known, but it certainly is a biggie if this wasn't done before.

• It's roughly known from where Sarazin's soldiers were coming. So what we do positively to the crusader villages, we do negatively to the opposing villages. If we constantly poison water supplies, (re)-introduce pox and cholera, steal and burn crops, interrupt or kill caravans, again and again all few years, over the course of 50 years this can severely shrink the numbers Sarazin will bring. He had maybe of 100 000 Soldiers when he ended the crusades. No tactic will ever be good enough to go against this, also not with 100 or 300 extra soldiers from the future. But 50 years are a long time.

• If that's too evil, send priests. Culture eats Strategy for breakfast. Convert people to Christians or at least convert them to people opposed to the ruling caste, build a network, when the day comes, have people inside the wall who attack the door.

Ok, you don't want all that? If introducing modern organization and tactics is not a forbidden technology, you could do just that.

Ancient armies used to stick together because it was wise to do so. Side effects are, to build up a camp site and to start again the next day was wasting hours. I can imagine that the first soldiers were arriving at the new campsite when the last soldiers were just starting their journey the same day. So there is some kind of "Soldierworm" in the landscape that is easy to see. The "Worm" is surrounded by scouts - they have horses, they are freed from the camp work, so they have additional valuable hours and speed to check the area. They will report in what they see, and if they don't report back, that's a message, too. The General might then send a small horse-unit that way to see if he can get the evildoers.

And here we have a use for our modern small-unit hide-and-seek tactics. Harass those scouts, maybe even fight the knights that come after them, then disappear as good as possible. Do that from all sides. I don't know how much damage they can do that way, but as they'd never fight 1-1 I guess they can do some things.

There is also a worm of civilian cars following the army, with food and water and smiths and prostitutes and everything a soldier might want to spend his money on. If those are attackable, it might be a juicy target indeed.

Finally, armies were used to not having any logistics. They were feeding of the villages on their way; often they were as bad for friendly villages as they were for enemy villages, just because they were using all the winter stock for themselves. I've read the Simplicissimus, a story written during the 30-years-war which was 500 years later 1618-1648. They STILL had no proper food logistic then. So I guess in the crusade, they also had those small units of soldiers with the task to "empty" the surrounding villages (friend or foe) to feed the army.

Attacking those might be efficient indeed. No General would send his entire army for food, those units are small, 10-50 people. And here we go. Kill one of those units, get away, kill the next, get away.

Getting away is the difficult part. You leave traces in those times. Rare is a road made of stone.