To be a tool of foreign policy a military must be able to attack. NATO isn’t.

We call it “NATO” and it has nuclear weapons.

(The canonical disproof was the lead up to WW2).

What actually happens is that each nation pursues its own interest, and to what extent those interests combine led to the formation of sub-groups in the larger group. We see this now with the UK and the new Eastern Europeans nations taking a tough line to Russia and the Germans, French and Italians taking a soft line.

In the interest in preserving harmony, all that can be done while remaining whole is the weakest common response.

Europe in its current form is not capable of meaningful action on the world stage. It is barely capable of immediate self-defence, let alone rising to the occasion where a tough stance with short-term costs is advisable.

One way to resolve this is to politically unify foreign policy. Let alone the question itself of whether this is desireable, I wonder even if this would solve the problem, since it would require individual nation states to fully give up foreign policy. I don’t see how this could occur while individual states retain national interests, since those interests will drive national foreign policy, subverting the supposed central foreign policy.

Personally, I’m inclined towards an economic integration for Europe, but not a political integration. This would require politicians to keep fully out of economics, which is currently only a dream of a liberty which does not exist.

In short, somebody gave in to wishful thinking.