The idea of the EU, and one of the few ideas hatched by politicians that actually worked out 100% perfectly, was to intertwine and mix the economies of European countries so deeply that it would be economic suicide for anyone to go to war with a neighbor.
Germany and France have been at war, on and off, since the partition of the Frankish Empire into an eastern and western part, somewhere in the 9th century. Those (almost) 80 years of peace between these two countries that we had for the past (almost) 80 years are unprecedented in recorded history.