That's not the only choice, but to defend against a war started against you, you need to have people trained in that before the war starts. In other words, you

That's not the only choice, but to defend against a war started against you, you need to have people trained in that before the war starts. In other words, you need to identify the need to form up those forces before a war starts, even if you don't intend to ever start one yourself.