Extra Soldiers
Use the War command and select a general to enter into battle. Assign the maximum number of men to his unit. When the asked for confirmation for going to war, select the “No” option. Remove the general from the list of commanders and reassign him to the post. Return to the troop assignment screen. The number of men available should be increased by the number that was assigned earlier. Repeat this process to increase the number of men, but do not return to the main menu.

After accumulating enough soldiers, send several of your generals to war with 300 soldiers each. The extra soldiers will remain in service only if you win the battle. Note: If you bring more men into battle than originally present in the attacking province, there will be no men left in that province after the battle.