You are really completely clueless, I have no idea why you keep posting comments that contradict your own comments but fine, whatever.
There are four different mutual defense pacts in Europe and there is an umbrella one and they all operate independently of NATO. And then there is NATO, with or without the USA.
I assume the contradiction you refer to is that EU has this clause but it's still not considered a military alliance? Maybe you read the term differently. It doesn't mean it has zero defense dimensions, it's that its mission or capability are not military. That's why NATO is the one a would-be invader needs to worry about wrt military consequences.
In WW2, was there an existing organisation for a coordinated response? In the Korean War? Was NATO the organization that coordinated allies in the Persian Gulf War?
Of course military alliances can be formed after wars start, I'm not saying this couldn't happen in Europe. But it's different to have a military alliance existing responding to a conflict (or better yet preventing the conflict, as the military alliance served as a deterrent).
