Even after 1000 hours, I am still learning new things about this game. Is that a good thing? If you asked me, probably not. There are so many obscure mechanics -- some of which are extremely important -- that the game doesn't explain clearly. Because of this, I figured I should write down all of them and put them somewhere. In the event that I am not 100% sure if something is true, I will make it known to the reader.

All of the difficulty settings are pretty self-explanatory, save for the AI settings.

Campaign AI affects many things:
In format: Poor/Average/Good (i.e the values on respective difficulties would be 6/4/2)

Economy:
- Player tax inefficiency becomes more severe as campaign AI difficulty increases. The player can hold 6/4/2 "core" fiefs, i.e fiefs that do not suffer from tax inefficiency. Each "non-core" fief increases tax inefficiency by 3%/4%/5%.
-

Lord Armies:
Overall, on good campaign AI, and to some extent average, enemy kingdoms will be significantly more powerful and it becomes essential to take lords prisoner.
- Campaign AI mainly determines how fast an AI Lord can build up an army and replenish their troops. In code, this is technically done by determining the cost of recruitment. On Good Campaign AI, a lord will be able to completely recover from defeat after just a week or so. Whereas on poor campaign AI, you can easily get away with never taking a single lord prisoner throughout your entire game, on good campaign AI, I would recommend that you take enemy lords prisoner -- even upstanding and good-natured ones -- to prevent a constant stream of enemies.
- Campaign AI also determines their army's XP rate, which influences their army's troop quality.


It is a common myth that max AI lord party size is determined by campaign AI difficulty. In fact, it is determined by the "ideal party size" variable, which is determined by the player's level. In other words, max AI lord party size is the same across all difficulties and scales with the player's level. Practically speaking, though, Lord armies will generally tend to be bigger on good campaign AI because Lords can reach their max party sizes faster because of their outrageously buffed recruitment speed, and you will generally see more large armies. Additionally, these death stacks will have far more room to upgrade their troops.


Behavior:
- Campaign AI determines how biased lords are against the player in several ways. On Good campaign AI, lords will be less willing to follow a player marshal, less likely to join the player's kingdom, more likely to declare war on a player kingdom, and (I think) more likely to attack the player's fiefs.

TL;DR, don't play on Good Campaign AI unless you want a challenge, because the AI cheats a lot. On good campaign AI, a lord will essentially be able to spawn an army out of thin air, and in the late game, it wouldn't be unusual to see Harlaus walking around with nearly 100 men-at-arms. If you find Warband too easy then adjusting this setting might help.

-- COMBAT AI --
But what does combat AI do? It turns out that combat AI is a lot more simple to explain and a lot less cheaty than campaign AI.
On poor combat AI, the AI is stupid. They will delay their swings, giving you an opening to attack them. They will not feint and they are generally poor at blocking. Their sole tactic on the battlefield is bum rushing into your shield wall. I would not recommend playing on this difficulty. I played on poor combat AI for my first 800 hours, and it resulted in some very bad habits which I'm still trying to break. You will not get that much better at combat playing on this setting since everyone, even elite troops, are pretty much punching bags. This is probably the most noob setting to turn down, even worse than the damage settings IMO.
Average combat AI is a balance, I'd recommend it for new players.
On good combat AI, the AI will have no delay on their swings, will feint extremely frequently (several times before an attack), and is very good at blocking. This allows them to operate to the full extent of their stats, and everyone will fight as if their lives depended on it. It will be a challenge to take down even a single elite troop if your weapon proficiency is not good.

Using 2-Handed weapons from horseback or with a shield gives you approximately a 10%-20% penalty to weapon speed and a 10%-20% penalty to damage. The penalties are actually slightly different but roughly lie in the same range. According to some tests by some members on the Taleworlds forums, the attack speed penalty might decrease as your weapon proficiency increases (the guess is a 2% reduction in penalty per 100 WP). IIRC, the damage penalty was not shown to decrease. As far as I know, these two penalties do not stack.

The effect of the weapon's Speed stat (the weapon's stat, not your character's proficiency) is not a linear progression. The difference between 89 and 90 is bigger than the difference between 99 and 100.

So if you want to use a shield, a 1H sword that does 29 damage and has 99 speed is WAY better than a 1H/2H Sword that lists 35 damage and 95 speed, b/c with the shield, the 1H/2H is actually doing about 29 Damage but at like 81 speed (which again, is WAY slower than 99). - Ferox

A horse walking backwards can go straight up a cliff. Useful when you spawn somewhere awful.

If your power draw is 3 above the requirement of the bow, you get a huge accuracy bonus.

-- How do lords interact with the player? --
Lords have personalities. These personalities are: Upstanding, Good-natured, Martial, Calculating, Pitiless, Quarrelsome, and Debauched.
The better their personality, the more loyal they are as vassals, but the harder it is to convince them to join your kingdom. Ideally, you want all of your enfeoffed vassals to be either Upstanding, Good-natured, or Martial. A lot of people already know that, but my advice is to take on lords with bad personalities as well without giving them land. They will defect from you after a while but getting them on your side will prevent them from fighting for the enemy for a bit.
Their choice of dialogue depends on their personality, so once you memorize the different dialogue it becomes easy to know their personality. The wiki has a very helpful page that lists the different dialogues at the bottom of the page: https://mountandblade.fandom.com/wiki/Vassals#Personalities

Interestingly, AI Kings will not allow you to become their vassals under normal conditions if you have high right-to-rule -- they consider you a potential rival/threat to their realm's stability. You can still become their vassal if you take land first before asking.

AI Lords that dislike you will do everything in their power to attack your villages. The only exception is the Good-natured lord, which will never loot any village, ever, including villages owned by other AI lords.
If a sadistic (evil/debauched) lord dislikes you (-20 relations or less), they will hire assassins that attack you in taverns. They function exactly like a Belligerent Drunk does except they attack you without notice and you do not have to look at them for them to attack you.

-- Which skills can AI Lords use? --
If you plan on making a companion into a lord (which you can do if you ask them "Would you be interested in holding a fief?" when you have your own kingdom set up), you might want to invest into these for them. I highly recommend checking the wiki first, however, because companions have personalities as well. And you will lose a chunk of relations with every lord in the game if you make a commoner companion into a noble.
AI Lords use 4 skills:
- Pathfinding
- Trainer
- Tactics (helps them in autoresolve)
- Leadership

-- How are autocalc battles, both between you and an AI and AIs versus other AIs, calculated? --
1. Numbers. 2. The levels of their troops. 3. Level of the Tactics skill.
Equipment and so on has no role in autocalc. From what I understand, all that matters are those three.

-- Do AI Lords have wealth? --
The answer is yes. They use their wealth for recruitment (and possibly upgrading). Unlike the player, they have to manually collect money from their fiefs. This is why you'll see them sitting outside of their villages. It's also why AI Lords can become poor if they have too many disjointed fiefs -- because they don't have the time to travel around the map to collect taxes. For this reason it is best to arrange your vassals' fiefs in a way where each vassal only has a few fiefs, and each vassal has a "region" where their fiefs are all right next to each other.
An AI lord's village will lose wealth if you loot it, preventing them from collecting taxes. But that barely does anything compared to just defeating them in battle and forcing them to rebuild their army. A fief's wealth cannot go below 0.

The AI lord's economy functions completely differently from the player's economy. AI lords cannot have enterprises. As far as I know, their only source of income is their fiefs (They may, but I am not certain if this is true, get some money from looting villages).
AI Lords lose wealth by recruiting troops, and possibly from upgrading them.

-- Do Lords have to pay upkeep? --
The answer is yes. Lords pay wages to troops based on this formula: ((Troop_level^2)+50)/30. They do not have to pay extra money for cavalry or archers. If they cannot afford their troops, their troops will either get disbanded by the lord or desert from the lord's party.
Which troops desert from a lord's party is random. The lords disband low-level troops and non-faction troops first.

You may have noticed the small parties of fiefless lords. They aren't making money, so how can they have armies? The answer is that Lords don't only have a maximum party size, they also have a minimum party size. If they are below this, they will gradually get troops via free recruitment while sitting in a walled fief until they have a few dozen troops, say 30-50 or so. However, because they have no money, they will not be able to upgrade their troops or recruit any more above that minimum. And when they do get money, they will have to pay for all of their troops' wages, including the ones they got for free.
Hypothetically, an AI lord's army can be of an infinite size, because they can go over their max/ideal party size by rescuing prisoners. However they will eventually start struggling with desertion or they will have to disband the prisoners.
As far as I know, AI lords do not have any system of debt. Their fiefs definitely don't.

What is certain, though, is that Lords have to pay for recruitment above the minimum party size. How much this costs depends on Campaign AI difficulty. This is why on Good Campaign AI, a Lord can spawn an army out of thin air.

If all your lord has is castles then he won't have any wealth to build up his army since the wealth of castles goes towards maintaining their garrisons. Villages might not be good for the player but they are really good for the AI. A good setup for an average Lord is 1 castle and 1 village. Castles mainly help them raise their maximum party size, +40 each, rather than providing wealth. It should also be noted that a castle's wealth is based on its village's wealth -- this also applies for when the player owns the castle.

The interesting thing is that AI Lords do not pay for their garrisons. Instead, an AI Lord's fief's strength is determined by the fief's Prosperity. Coupled with the fact that AI Lords do not suffer from tax inefficiency, a lord could theoretically have every fief in the game and each garrison would be fully stocked. Actions that lower the Prosperity of a town, such as destroying caravans, will, in the long-term as the fief changes hands, result in a weaker garrison, but this is not practical knowledge to the player. It does generally mean, however, that places that are bandit-infested, have been sieged countless times, and so on should have weaker garrisons, at least if the town's situation remains consistent throughout the entire game.

-- Do Lord armies use food and morale? --
No, they don't use either.

-- How do AI Lords manage their armies and garrisons? --

As stated before, AI Lords do not pay to reinforce their garrisons.

AI lords' troops need XP to be upgraded. An AI lord will add 30% of (Trainer+2)*500 xp/every 2 days. Lords have trainer skill between 2-7, on average this is around 3 or 4. So the average lord adds ~375-450 xp per day. Each point of trainer is worth 75 xp/day. This is rather meager -- a Player Character with 10 in trainer adds 80 xp to each unit. I don't know for certain if it costs an AI lord money to upgrade a troop, but I highly suspect and assume that it does.

How is a Lord's troop quality determined? The short answer is that an AI Lord's number of elite troops depends on his wealth (an AI Lord requires wealth to upgrade). Again, because higher Campaign AI will reduce recruitment cost, Lords will have more money as a side effect (saving money is gaining money in this case) and they will have more money to upgrade troops with.

Without tweaks or cheats, the attribute cap is 63, the skill cap is 10, and the proficiency cap is 699.

With tweaks (like TweakMB), you can increase the skill cap to 15, but the game is hardcoded in such a way that it is impossible to increase it past 15, no matter what modding shenanigans you try.

I'll get right to the most important tip: THE +4 BONUS THE PLAYER GETS FOR LEVELING PARTY SKILLS DOES NOT REQUIRE A COMPANION TO HAVE THE SKILL!
If you have 10 pathfinding, you will get the 10(+4) even if not a single companion in your party has a point of pathfinding. You can test this by starting a new game, importing a character with 10 in every skill. You will notice that you have +4 in every party skill despite no companions being in your party. This means that if you are playing a brainy character, you will only need a couple of INT companions so that you can get them to 10 in the party skills that you don't plan on leveling.

If you need advice on leveling companions, I would suggest two things: Bandit camp quests and hunting down bandits with just your companions in your party.

Approximately 1/5th of strength is added to your damage output. This means that every 5 points of strength will increase your damage by about 1.
Every point of agility gives you an increase in movement speed approximately equal to 1/4 or 1/5ths of a point of athletics.
Every point of agility gives you 0.5%+ attack speed.
Persuasion increases the chance of routed enemies surrendering, meaning they become prisoners in your party without you having to fight them.

Each point of weapon proficiency slightly raises attack speed and damage.
On average, every 100 points of proficiency will increase attack speed by about 6% -- I have heard some say 6% and others say 15%, but I chose the 6% because that is according to the modder Leonion, who I trust quite a bit. Additionally, with melee weapons, you get a damage bonus of 15% per 100 weapon proficiency above 100. It's multiplicative with Power Draw/Throw/Strike bonuses.

Loot is divided up among the player's army using a system called "shares". The player gets 10 shares, each companion gets 3 shares, and each soldier gets 1 share. As you can see, your companions steal a lot of loot so I would not recommend using them in the early early game as it will hurt the money you get from the first few bandit parties. However, it is still absolutely worth getting all your companions before the mid-game starts -- once you secure a meager amount of wealth -- because Companions are very useful as trainers.

Quality of loot is determined by which troop stack in an army you attack first. So, say you're going up against 500 looters and 100 Swadian Knights with a small army of 50 or so. If the first person you kill in the battle is a looter, your loot will be absolute garbage. But if you kill a Swadian Knight first, your loot will be much better. This only matters in very large battles where the player is outnumbered.

-- Campaign Map --
Hold down CTRL+SPACE while moving on the campaign map to speed up game time.
CTRL+Left click on items to buy and sell quickly at merchants.
-- Battles --
If you attack in the direction you're being attacked right as soon as you're about to get hit, you'll parry the strike. This is known as the "chamber block".
Press E to kick. Pretty dangerous because it makes you drop your shield and become immobile for a moment. Not the most applicable to PvE.
Pressing Backspace in a battle will give you a minimap and allow you to control your troops by clicking on the minimap.
You can also hold down F1 in a battle and you'll be able to drag around a rallying point, which allows you to control your troops. You can make separate rallying points for each group.
Switch between control groups by pressing 1, 2, 3, etc. You can assign troops to control groups in the party menu.
Certain weapons, especially throwing weapons, have multiple attack types/styles. X swaps between them. Try it with a throwing axe or jarid.

Keeping horses in your inventory will reduce the party speed penalty for carrying heavy things. However, an excess of horses in your inventory will just slow you down and take up needed inventory space. I personally prefer 3 horses. Quality of the horse doesn't matter for this bonus, 3 lame saddle horses will be just as good as 3 spirited coursers.

The player can heal lame horses by keeping them in their inventory. This is important because there is a chance of your horse dying if it gets downed in combat while lame. Unfortunately, you will not recover positive modifiers (such as Spirited) after healing your horse. How long it takes for the horse to heal depends on the party's wound treatment skill.

Similarly, your shield can get damaged if it breaks too many times. I believe that it can break completely as well if it keeps breaking after getting damaged. Unlike horses, you cannot repair/heal shields.

The recruitment option for a village is reset by a relations change. What you can do is recruit, then take a quest and recruit again, then fail the quest and recruit again, then take another quest and recruit again, then fail that quest and recruit again... You can easily get 50+ recruits from a single village this way. Most of your companions will complain about failing a quest, but unless they are already extremely unhappy, they won't leave.
I would recommend getting to 100 relations with the village before doing this. After that, you use the failing quests strategy until you're down to 90 or 80. It's not too hard to get back to 100 again from there. Then repeat.

Additionally, if a village has low prosperity, you can ask the villagers "How is life here?" and one might ask you for a donation of 300 denars in exchange for 1 relation point with the village. While this does not appear to be a meaningful amount, as I discussed above, a relation change with a village allows you to recruit from them again.

If you have high relations with a village, there is a chance of you getting higher-tier troops from recruitment with them. If you are really lucky, you could even end up recruiting elite troops, like huscarls from a Nord village, without having to train them. I have heard of two stories of getting 50+ Huscarls from a village, and one story of someone getting dozens of Swadian knights from a village. If I recall, the chance of getting higher-tier troops is affected by the village's prosperity.

-- Marriage --
If you visit a lady before you get permission from her guardian (father/brother/etc, whoever mentions her when you ask if you can cement an alliance), the guardian won't give you permission to visit or marry her. He'll say "I've heard that you've already been speaking behind her back, don't speak to me about her again" when you ask. You might think the only way to marry the lady by that point is to elope, but it turns out, you still have a chance. What you should do is improve relations with the guardian up to 100. After this, try to find the guardian at a feast. Talk to him at a feast and he'll basically give you permission when you greet him.

-- Founding a Kingdom (or, alternatively: What is Right to Rule?) --
If you go straight to creating your own kingdom without being a vassal first, you'll probably have low right to rule. As a king, low right to rule increases your chance of getting declared war on and also makes it harder to get Lords to join your kingdom. You raise right to rule by being a vassal (or king) of a kingdom when a peace treaty that involves the kingdom that you're a part of is declared. You can also raise it a bit by getting married.

The meta isn't the focus of this guide. Mainly this guide is just meant to be a collection of interesting tidbits of code and numbers. But I'll go over the meta real quick because it might be helpful for some people.

There are two mainstream metas for character and companion combos:
For combat characters supported by INT companions, you generally want to build your character as a heavily armored horse archer with a melee weapon as a side weapon. So you could go Bow+Arrows+Arrows+2H sword, or Bow+Arrows+Sword+Shield. Horse archer builds excel in prolonged battles, and theoretically, as a player, you could solo an entire army by yourself if you had enough arrows with you. I do not recommend getting 10 horse archery, most experienced players I've seen suggest 4-6 as the ideal amount of horse archery.
For commander characters supported mostly by combat companions, you want to prioritize three skills, the "Trinity" of skills: Surgery, Pathfinding, and Trainer.

For commander INT characters I would still put a few points into trainer on each of your companions. And your couple of INT companions should have 10 trainer for sure.
If you go INT, you might want to be using a crossbow because bows aren't very good unless you have a lot of STR and power draw. You should also give your INT companions crossbows.

If you go INT, I would recommend putting a few points (3-6) into Persuasion, but 10 is not needed. It helps you marry earlier, hire mercenaries cheaper, convince lords to defect to your kingdom, and convince routed enemies to become your prisoners. The only effect that Persuasion has that really matters from a meta perspective is the defection one.
If you are having trouble getting lords to defect, I would recommend raising your right-to-rule to max (99). It will make the "ancient laws and customs" option for lord defection very powerful. If you are still having trouble, stack relations. Generally speaking, the longer the game goes on, the higher the relations honorable lords will have with their lieges, and the harder it will be to recruit them.

CHA is probably the worst stat for the player character to focus on. A CHA build is useful for newer players, since 10 Leadership allows your armies to be larger and require less weekly upkeep. But an experienced player will have no issues with party size or money. I would consider a CHA build a "training wheels" build.

All skills in Warband are useful to some extent, but not all are equally useful for the Player. The "non-meta" skills are Power Throw, Tracking, First Aid, and Trade.

For Tracking, just have a companion with a few points in it. Even then it is non-essential. From my experience, tracking is often considered the least useful skill by experienced players.
For Trade and First Aid, it helps to have a companion invest into it, but the player should avoid investing into them.
In my opinion, 10(+4) engineering is overkill, so I would recommend investing into it with a companion.


For armies, the meta is pretty simple.

In the field, Swadian Knights/Mamlukes > everything. Heavy cavalry dominates the meta, both in Native and nearly every single mod I have played. If you do not like the heavy cavalry meta, I would suggest the Viking Conquest DLC.

As far as sieges go, you pretty much always want Huscarls and Rhodok Sharpshooters. There are situational exceptions, but overall, those are the two best options. Swadian knights will work about as well as huscarls, but they are far more expensive.

Situational exceptions: Vaegir guards can work as the defense in certain castles and cities. There are also certain castles and cities where archers have the potential to perform better than crossbowmen. However, vaegir guards don't have shields, and vaegir archers don't duck like crossbowmen do, making them a step below overall and generally situational.


Equipment-wise:
You always want heavy armor. Light armor will not benefit you in sieges or on horseback.

Bows:
For the combat build, you may be wondering which bows to use. Attack speed with a bow increases with proficiency and ammo is limited, so you generally want to prioritize high-damage bows over high-speed bows. However, I would wait until you develop good proficiency with the bow before doing this or you'll be way too slow. The war bow is definitely the best bow in the game, but it takes a lot of proficiency to use effectively because of the slow attack speed.

Throwing weapons:
Throwing weapons are useless past the early-game. They simply don't have enough ammo to be practical. You should still invest some proficiency into throwing weapons for tournaments, though.

Melee weapons:
I'm not going to go over all the melee weapons. Instead, I'm going to give you a general criteria for what you're looking for.
Do you fight on horseback? Avoid weapons with short reach.
Do you have low proficiency? Use a weapon with high attack speed until your proficiency gets higher.
Are you in the late-game? Keeping a weapon with short reach handy in your inventory might be useful for sieges.

As with bows, attack speed will increase with proficiency, so fast attack speed kind of falls off later. Despite this, you don't necessarily want a *slow* melee weapon, because melee combat requires fast reactions.
There are plenty of good 1H weapons. There isn't one that stands out in particular -- it all depends on what you're looking for.
1H weapons are good for the early-game because you'll be able to equip a shield. A shield can be helpful in the early-game because you haven't purchased any good armor yet.
2H weapons can be very powerful, but they make you vulnerable to archer fire. You will have to stick around your troops and use them as a shield.

If you know of any hidden values that I did not include, or if you have any suggestions or corrections to make, you can suggest them in the comments. If possible, please provide evidence from the code or from a video.

As far as my credentials go, I consider myself an experienced player (I have 1000+ hours) and I have prior modding experience with Warband, so I am familiar with some of the code. However, most of this information comes from experienced players and modders discussing code and answering questions about mechanics on the TaleWorlds forum and Reddit. Special thanks to Leonion for all the helpful posts he's made on the TaleWorlds forum. Special thanks to Ferox for his many helpful additions via the comment section below.