Money on its own won't win you wars, but you need money to even be able to fight. Sure, you may be able to replace some of the money with slave labour, levies/c

Money on its own won't win you wars, but you need money to even be able to fight. Sure, you may be able to replace some of the money with slave labour, levies/conscription, but you still need enormous amounts of food, materials, supplies and people, and a lot of that does require money, unless you've managed to completely eradicate money from your society.