War within the EU is really really unlikely. A successful part of the EEC/EU is integrating the economies of its countries to such an extend that war becomes economically un-viable.
Nowadays war between France and Germany is close to as absurd a thought as a war between Calafornia and Texas is. It's not remotely comparable to 1900-1950.
Russia is the largest threat for European countries, but currently an attack on a NATO member seems unlikely.