Mount & Blade II: Bannerlord

You can do this with ease defending a fief but is a gamble and it is a waiting game the chances of you defending by having 500 less it’s pretty low unless you’re willing to dismissed some of your troop until you’ll get 500 less troop . If you do get that chance do it you can always save before battling and load up if you failed. Tip: if they already start to climb on ladder just grab the stone near onager dropped it on them you’ll get over 10 kill with 1 drop. Try to go where’s that onager and never use onager the bot will use it better than you

Tbh this is easier when you’re over level 25


Other method:

It is require for you to have skill levels in engineer I had my 116 when I did this and I did it against a kingdom that was weak with 2 fief lefts . Most importantly you need to have about 600+ influence just build an army make it big as you can so you don’t get attack while doing this. Go head attack any enemy fief over at least 800+ defender. Then make sure you build trebuchet repeatedly and keep recovering the one that got destroyed until wall defense goes to 0 (Do not make siege tower or ram it slowed you down from building trebuchet) . Once the wall health is 0 go press B leave the siege and save right away just in case . After disband some of the lord in your army until you have 500 less troop. If you don’t have 500 less troop yet you can kick some of your own troop until you have 500 less . Then go lead assault since your army is outnumbered try kill as much as possible at least 30+ . I actually had 124 kill on my battle I just keep picking up those stone near that onager keep throwing at them while they’re piling next to each other (it does crazy area of effect and damage )

(But that way there will maybe be more 2 battle to win with me was only 2. After you complete all the battle you’ll unlocked the achievement)

I had a save where i was defending a castle with 204 guys vs 754, did the defense and it did not pop, i’m assuming because the enemy retreated.

Reloaded the save and simmed it, and popped instantly.

Never had the opportunity to do a 1500vs 2000 land battle but that would likely be easier

Since previous posters only suggested doing it while defendig a castle (which can be a bit of a tedious random waiting game, since you need to get besieged by a big enough force and need to wait through the siege until they attack without an ally army coming to your aid uninvited), I thought I'd share how I did it in a field battle. I beat a force of 1100 with only about 250 troops on realistic difficulty using this tactic.

There certainly is more than one way to win field battles against overwhelming numbers, but probably the easiest one is using a small elite force of 200-300 Khuzait Khan's Guard. Khan's Guard are very overpowered tanky horse archers with lots of ammo who can also do double duty as close combat cavallery if you order them to hold fire (f4), which makes them use their glaives instead. When they are toggled to close combat mode, they can even go toe to toe with elite cataphracts and win.

Prerequisites

To be able to beat an army with more than 800 troops with 200 Khuzait nobles, we need the following prerequisites:

- a force of 200-300 Khuzait nobles, ideally all Khan's Guard, but it doesn't hurt if some of them are still Keshig or Thorgud (their tier 6 and 5 versions), since those are already quite strong and use basically the same weapon setup. Just don't have squishy Quangli or Raiders in the mix. You also should have two clan members who are experienced horse archers (optionally including yourself), so they can buff your horse archers skill and damage output with their riding and bow perks. Also you should have unlocked the perk on the leadership skill tree that prevents tier 3+ troops from ever fleeing, because otherwise even Khan's guard can get nervous when they are outnumbered 4 to 1 and start to take some losses.

- an enemy army that is infantery-heavy, has a good amount of inexperienced units in the mix and has less cavallery than you. They can have a good amount of ranged troops, we can deal with those as long as they aren't all elite units.
Your best chance to encounter such an army is when the enemy already had their first big army defeated in the current war and hastily assembled a second one (with a big share of freshly recruited troops).

- a map with wide open terrain (open flat plains or soft hills with few trees or a desert map with all sand dunes) and daylight. The battle map that spawns can be a bit unpredictable sometimes, but the general type of battle map you get does correspond with the stuff that is nearby on the world map, so if you confront the enemy on open plains or desert with no mountains or settlements nearby, you are very likely to get a suitable map. Luckily, your horse archers only force will be a lot quicker than the enemy army on the world map, so you can lure them into favorable terrain.

How to run the battle

1) Starting preparation

During the preparation phase, split your horse archers into two roughly equally sized groups and assign each of them a good horse archer captain (but don't delegate command, the AI is not smart enough to outmaneuver the enemy to the extent that we need to do.) Set both of them to loose formation (f2+f3), which will cause them to take less hits from enemy archers and always be clear to shoot (if you use line formation or any tight formation, only those in the front will shoot). Place them a little apart and order one of them to follow you (f1+f2)

For the rest of this guide, I'll refer to the group that you have following you around as team 1 and the other one as team 2

2) Getting rid of the enemy cavallery

If the enemy has any noteworthy cavallery force at all, we'll need to destroy those first, because they can intercept us and do serious damage when they catch us off guard. When we have our troops clumped up in one group, the AI cav is usually smart enough to avoid them by running circles around their foot troops, so we need to bait them out. Send team 2 to a position away from team 1 just in range to take shots at the enemy force. When the enemy cav starts making a beeline for them, order them to retreat to a position further back to lure the enemy cav away from their infantery (use f1 and point to position rather than using the fallback command, we want control where they move and we want them to start moving when the enemy cav isn't too close yet).

Once they lured the cav safely away from their main troop, command them to hold fire (so they'll use their glaives) and rush down the enemy cav (point on unit and f1+f3) team 2 will now engage the enemy cav and we rush to help them with team 1. Also order them to hold fire, but don't use F3 (which causes them to scatter), it is much more efficient to lead the charge and draw them behind you. That way, team 2 will with full force crash into the enemy cav that is already engaged in battle with team 2. Just keep in mind that it is crucial that you don't fall, so maybe don't plunge into the biggest mass of enemies yourself, but veer to the side shortly before contact and run a small half-circle around the combattants. (This is assuming that you have a fast top tier horse and thus are some way in front of the team that follows you). Once team 1 crashed into the cav, have them F3 on the cav, too.
They now should make quick work of the enemy cav, just keep an eye out that the enemy infantery doesn't catch up and pull your troops out of attack mode before they start to scatter to chase single fleeing survivors. Fastest way to pull your troops out when the enemy infantery gets too close is to order everyone to follow you and charge a good distance away, where you can split them up again and regroup at good positions.

3) Getting rid of most of the enemy archers


Archers on foot in loose formation have an edge over horse archers in ranged combat, because they shoot much more precisely than moving horse archers and they make smaller targets, so we want to decimate them quickly before we deal with the infantery.
Have team 2 take a good position to shoot at the infantery (ideally on a hill slope, but in any case not too close) while keeping a higher distance with team 1 (can still be in shooting range, but doesn't have too. If you are concerned about running out of arrows, you might even have team 1 hold fire here). Have team 2 move back to pull the infantery behind them. The archers will fall back, because they will stand and fire as long as their targets are in range. Now have team 1 follow you and hold fire while you quickly circumvent the infantery and then rush straight through the archer line from the small side of their formation. To avoid being shot down, make sure you go at full speed and do a little zig-zag line instead of riding straight towards them. Veering just a little bit left and right in quick succession is usually enough to make almost all arrows miss you. Team 1 will follow right behind you and plough through the whole ranged unit, killing many of them and likely causing enough moral shock to make the rest of them flee. Don't stay to mop them up, get away in time to not be cornered by the infantery that has now likely turned to help their archers (and by this conveniently turned their back to our team 2, making a great target for them :-) ).

Rinse and repeat step 3 if necessary, but unless the enemy has a big number of elite archers, once should be enough to kill most of them, with the remainder not being a big threat for our heavily armored Khan Guard).

4) Destroying the infantery in the crossfire

With the enemy cav and most of their archers gone, we are now free to run circles around the enemy unhindered, but we still need to be careful. We must avoid getting stuck in close combat with an infantery force that still heavily outnumbers us and we must make our arrows count, since they will eventually run out. To avoid getting most of our arrows stuck in shields, we need to take the enemy into crossfire. Send team 2 to one side (ideally up a little hill) and take the other side with team 1. Ideally you have team 2 standing stationary, while you keep getting close-ish with team 1 following you (but without making contact), then pull back to draw them away from team 2. When you're far enough away that they turn again to go towards team 2, take a few shots at their backs standing still, then rush at them again to make them change direction again. This might not always work smoothly, so be on your guard and be ready to order team 2 to pull back when the enemy is about to reach them. If shit hits the fan and one of the groups does get engaged in melee, pull everyone out fast by making everyone follow you, get a good distance and regroup.

In case your troop should get reduced to less than 50 total standing, it can be better to have both of them follow you and ride circles around the enemy at top speed instead of keeping up the crossfire. This will usually mess up their shield formation, too.

Towards the end, you might run out of arrows, but at that point you should have reduced the enemy numbers greatly and their morale should be very low, so you can mop up the rest by using your Khan Guard like close combat cav. Have them follow you, crash through the enemy at one side (not the biggest pulk in the center) and then turn around and crash into the back of those who now swarm the part of your force that got stuck in melee.

5) During all of this: Stay alive and help

I may have mentioned once or twice that it is absolutely crucial you stay alive and concious until the last phase, since this tactic falls apart when you aren't up to command your troops. So you need to be cautious, but you can still help. To avoid getting knocked out, ALWAYS keep moving when you are near enemy cav or archers. As a fast rider, you are very hard to hit and you can usually dodge enemy cav coming at you as long as you keep your eyes peeled. Never risk to crash into an enemy force that is facing you, avoid getting stuck at all costs. Instead, you can attack enemies from the back while they are already engaged in melee with your troops (especially during the phase when you fight the cav) and of course you can use your ranged weapon of choice and take potshots at the enemy, ideally where they are standing in a tight group and don't have their shields turned toward you in a orderly fashion. You can also make a big difference if you can sniper or catch enemy banner bearers early. Just don't get too caught up in killing enemies personally, you don't want to miss the right moment to pull team 2 back.

My character was a horse archer build, so my loadout for this battle (as for most in that playthrough) was a noble bow, two quivers of stacked bodkin arrows and a glaive for easy ride by kills (the glaive has great reach and can oneshot just about anyone when you hit them with a swing riding by fast. Its relatively low damage stats are misleading, because due to its length, you always get a lot of momentum bonus, even if you aren't moving that fast.