If Europe has to, it certainly has the ability to fight any war. Europeans have been very successful at solving conflicts through soft power though and will prefer diplomacy over military action at any time. That does not mean that Germany, France, Britain and 27 other EU countries would not be able to put an impressive army on the ground would they see the necessity to do so. And I have to disagree about Russia beeing a threat. I firstly have not seen Russia making threats towards western Europe recently ( and they would be extremely foolish to do so), and secondly you seem to underestimate the factor of economic interdependence in Europe. As much as Europe needs russian oil and gas Russia needs foreign investions and export markets. To move agressively against Europe would be economic suicide for Russia and I see no indication of the russian leadership beeing lunatic enough for such a move. Russias behaviour towards former soviet republics is a different story but Russia attacking the EU is not an option. Not really.