What were some of the causes that led to the formation of the eu

The EU means the European Union, correct?

Some of the causes for the formation of the EU was a struggle for a peace on the continent: in a Union, attacking another country would be a blow to one's own economy. If the European nations were more united then there would be a smaller chance for another war in Europe: and this thinking has proven to be correct.

Another reason is a stronger economy for all the nations involved.