The self-destruction of Europe during World War I was accompanied by a 15 per cent growth in American production. Amid the chaos of the old continent, the United States discovered an important outlet; Europe had to import masses of consumer goods, means of production and arms from America. Once the war ended, the reconstruction of Europe proved to be the new and important outlet. Through massive destruction with an eye to reconstruction, capitalism has discovered a way out, dangerous and temporary but effective, for its new problems of finding outlets.
During the first war, the amount of destruction was not 'sufficient'; military operations only directly affected an industrial sector representing less than one-tenth of world production (around 5-7 per cent) . In 1929, world capitalism again ran into a crisis situation.
As if the lesson had been well-learned the amount of destruction accomplished in World War 2 was far more intense and extensive. "All in all therefore during the second world war almost a third of the total industrial sector of the world was drawn into the direct arena of military action." 
Russia, Germany, Japan, Great-Britain, France and Belgium violently suffered the effects of a war which for the first time had the conscious aim of systematically destroying the existing industrial potential. The 'prosperity' of Europe and Japan after the war seemed already foreseen by the end of the war, (Marshall Plan, etc...).
Contrary to common opinion, 'reconstruction' does not stop when the ruined nation regains its pre-war levels of production: reconstruction does not only involve the directly productive goods but also all the infra-structures and means of life destroyed during the war, even though their reconstruction is not immediately necessary in order to attain pre-war production levels. Reconstruction is never undertaken with pre-war technology; important progress in productivity and the concentration of capital has occurred during the war. Also, the fact that the former levels of production are regained does not necessarily mean that the same mass of value will again be tied up in productive capital. Finally, during their destruction those countries concerned became industrially backward in relation to the other powers. Their reconstruction cannot be considered completed until the moment when they regain not their former levels o production, but ones which make them again internationally competitive.
In this sense, reconstruction characterised the growth of the post-World War 2 period right up to the 1960s and not just to the 1950s as is often supposed.