"War is not the answer"

Well, at least it's not the answer to some questions.

To the question of, "What is 2+2?" "War" is definitely not the answer.

To the question of, "How do we defeat Hitler?" or "How do we end slavery in the US?" "War" was certainly an answer.

Bumper stickers all over the map claim that war is not the answer. What question are they asking?