From the ancient times of the Greco-Roman period on to the Middle Ages, the Industrial Revolution, and later, efforts for a united Europe were promulgated on many occasions. Writers and rulers in ancient Greece and Rome supported or enforced, from time to time, unions of city-states for parts or the whole of Europe. For centuries, emperors, kings, feudal lords, theologians, artists, and many common people vainly yearned for unity among the divided and, in many cases, belligerent nations of Europe.
From 1815 to 1854, five European powers ( Britain, France, Prussia, Austria, and Russia) formed some kind of alliance (Concert) after the Napoleonic wars that reduced conflicts and kept peace for 40 years. Also, they established buffer zones, held regular conferences, and undertook joint actions, including military operations so that costly military buildups could be reduced and domestic economies strengthened.
After World War I and particularly at the beginning of the Great Depression, new totalitarian fascist governments came into power all over Europe. The end of the depression of the 1930s came finally with World War II in 1940-45. Thereafter, mostly labor parties came to power in western Europe. They introduced reforms regarding distribution of income, extension of welfare services by the state, and nationalization, particularly in railroads, power, coal, and other heavy industries.
The European Economic Community (EEC) was established by the Treaty of Rome in 1957 with six members: Belgium, Luxembourg, the Netherlands, France, West Germany, and Italy, commonly known as the "Inner Six." It was formed to gradually reduce internal tariffs. Because the group was successful, the United Kingdom and Denmark, as well as Ireland, joined the EEC in 1973.