Just-war theory is useful if it’s interpreted properly.
Take the principle of proportionality, for example:
Combatants must make sure that the harm caused to civilians or civilian property is not excessive in relation to the concrete and direct military advantage anticipated by an attack on a legitimate military objective.
If the enemy’s objective is the destruction of your nation — civilians and all — it is just to seek the destruction of the enemy’s nation — civilians and all.
Thus endeth today’s lesson in how to wage war.
Politics and Prosperity 