My friend, that depends on who the enemy is. If they're facing Russians then yes. If they face you, then yes. But one on one, they will never cooperate with each other unless egged by US.
It remains to be seen.
With EU disintegrating economically and with no wars to boost scalable level of weapons production, the cost of European weapons has become exorbitant compared to cheaper and more battle proven weapons from USA and Russia. When there is no war to fuel unity and integration, it is just a matter of time when different countries disintegrate in their alliances and pacts.
I might sound philosophical but it is true.
Think about it. UK and France maintain their own strategic weapons arsenal and are permanent members of the UN. Why is Germany not allowed to wield its own ballistic missile arsenal? It was never allowed even though they invented the whole concept in modern warfare.
Because while Germany, France and UK show to the world that they wave hands together, both France and UK have their guns pointed at Germany behind along with Uncle Sam.
Germany is also the only country among the three to host an air force and an Army base of the US despite UK also being a member of NATO.
Why?
Because the former Allies are still worried about Germany even after all these years of war.
I agree with you that economic inter-dependency and better trade relations might have cooled down the simmering tempers of war and reduced any threat of a head on full blown collision, but not enough to not dislike or suspect each other.
EU security treaty is just an extension of NATO agreement.
Tell me, apart from these three countries above, who has the power to stand up against a massive enemy?
Rest of the countries are simply manpower for The Big Three. Perhaps Sweden and Finns can contribute as well since their doctrine was always to take on much larger and more powerful enemies.
Face it; due to German's weaker political position in military thanks to the other two big guys, there is simply no one else (maybe Sweden and Finland to some extent) who can take on a combined assault on Europe.
Even Turkey is in a much better position (apart from the German level of self-reliance which I am sure it will gain in the coming years).
