Battle Size Unlocker is a free and open-source mod for the game Mount & Blade II: Bannerlord. It allows you to set a higher limit for the size of a battle. It is perfect for campaign or sandbox battles and custom battles.

This mod is very easy to install and use, but it requires you to first have ModLib to allow you to edit in-game options. For manual installation, simply extract the downloaded file into your Mods folder. Then, activate the mod's module at the game launcher. Make sure that you keep it just below the official TaleWorlds modules and ModLib.