Mount & Blade features open-field battles between large forces, where you can fight bandits or enemies from opposing factions. You'll also participate in sieges, where you either defend or lead a charge against a castle or walled city, using a ladder or siege engine to mount the wall and penetrate into the interior.

Battles can be very large, with armies of thousands facing each other. It'd be a chaotic slaughter if all these men fought simultaneously, so open-field battles are handled in several pitched battles, in which forces of 20-or-so men face each other. Sieges are handled in much the same way, and in both fights reinforcements will arrive for you and for the enemy when losses mount up. There are no save points in between battles, nor are there any healing potions, so you can expect plenty of casualties. You have to be careful how you handle your all-important main character, too, as he serves as your commander by giving orders to infantry and cavalry to charge or stay back (orders which don't occur if said commander is unconscious). If you choose to let your troops continue fighting without their commander, the results of the chaos tend to be more negative than if you just let the battle take place in front of your eyes, even if you don't get involved – at least, this is the case if you're using heavy cavalry (hired blades and knights).