The intellectual and political roots of Western Europe’s post-World War II integration process in Europe reach to post-World War I period. Two world wars had brought physical destruction, socio-economic dislocation, and global decline. Breaking this cycle of self-destructive behavior required overcoming the Franco-German antagonism. As early as the 1920s, smaller and middle countries in Western Europe grew concerned about Soviet expansionism and the obstructionist policies of the United Kingdom. But London insisted on its unfettered great power status in Europe beyond well beyond WW II. From 1947 to 1961, it tried to impose its views on the integration project. Given its waning global influence, it was forced to ask the West European continentals to join the integration project afterwards. France was the most consistent proponent of integration since the 1920s. With the encouragement of the United States, it shaped European integration after WW II with the double goal of restoring itself to great power status and of holding an integrated Germany down after having fought three wars with it in less than a century. The role of the United States was crucial for the success of post-World War II integration.