Not an European army, but why not some sort of European NATO; at least between Western European countries (France, Germany, Netherlands, Italy, Spain, Ireland, Croatia, ...) since I think Russia don't want to have its army under a foreign rule. Our armies need some cooperation, because they aren't (yet) powerful enough against our common enemies (mostly the USA).
This already exists between French and German armies (
Brigade Franco-Allemande / Deutsch-Franzosische Brigade) : more than 5,000 French and German soldiers in Müllheim, Donaueschingen and Immendingen (Bade-Wurtemberg) are under common Franco-German rule. And don't forget
Eurocorps (France, Germany, Luxembourg, Belgium and Spain), but under NATO's rule.
I like its flag though :
