Europe has been at peace for the past 50 years for only one reason.
Because it was divided up between two superpower hegemons that kept their client states in check. Had it not been for the threat of MAD by nuclear weapons, the USA and USSR would have come to blows using their European pawns as front line troops. Now that the Soviet Union is no more and Euro/American ties are becoming weakened and strained, it shouldn't be too long before it's business as usual in Europe. The EU is another Yugoslavia waiting to happen. Remove the strong arm and the factions reemerge.