I don't see the difference between sending 20000 and 200 against a negligible defense if you can choose to not use munitions in battle. Either way the attacker doesn't spend anything.
Without a lower minimum you have very little damage being done in wars involving smaller sized nations, nations who should be able to rebound from infra damage more easily than nations with more infra.
I'm not saying 50 infra, but it shouldn't be 2. If my battle that I supposedly "won" and that I expended 6 hours of war points for can be covered 10x over with the income my opponent gains in a single turn, then it's not a win.