The Idea of a united Europe has existed in one form or another since the ancient Romans, which conquered a large amount of land in Europe, the romans might have wanted to conquer the whole continent, if not the whole world, but their empire fell before they could have managed something like this. This great empire, left a big hall in wester Europe, and great barbarian kingdoms of Germanic origin formed in its place.

The Germanic kingdom that formed in the province of Gaul, stood out from the rest. The Frankish kingdom, expanded its domain into large parts of Europe. By the year 800, the king of these Franks, Charlemagne, was crowned by the pope, as Emperor of the Romans, this was intended to be a revival of the great ancient Roman Empire, and to unify Europe and the Emperor and the Catholic Pope. Charlemagne is sometimes called the Father of Europe, that is not only because his grandsons divided his empires, and this divisions can still be felt today, but also because he initiated the Carolingian reneissance which brought back elements of Roman culture, and combined them with Christian ones, this was the basis for much of the European Culture to come.

Ideas of European unity appeared in more modern sense, with the enlightenment thinkers and their ideas in the 17th and 18th century. And was put in to practice after the French Revolution, where Napoleon's armies had managed to conquer much of the continent. The Corsican general had great plans: "I must make of all the peoples of Europe one people, and of Paris the capital of the world" unfortunately he failed and nationalism became the norm in Europe. 

This nationalism turned into national Socialism and Fascism, which were evil forces, bringing distraction in Europe. By the end of the war Europe lost its statue as the world superpower, millions of soldiers and civilians died, and over 6 Million Jews lost their life in concentration and death camps. 

After WW2, the leaders of Europe, from countries that fought against Germany, came to the conclusion that Europe must be in peace, because they can not afford to fight another war as devastating as WW2. 

"It
is to re-create the European family, or as much of it as we can, and to provide it
with a structure under which it can dwell in peace, in safety and in freedom.
We must build a kind of United States of Europe.” Winston Churchill

In time, the modern European Union was born.