The most positive effect of World War II was that it brought about the defeat of a number of truly barbaric regimes, most notably the Third Reich. It is undoubtedly the case that, without some kind of concerted military action, it would've been impossible to stop Hitler's racial empire, with all the suffering and barbarism it brought to tens of millions.
The War was also necessary to finish off the plans of Imperial Japan for its own racial empire in East Asia, which it pursued with utter ruthlessness. By destroying these regimes once and for all, the War helped to make the world safer for democracy.
In the United States, the War had a positive effect on the economy in that it ended the scourge of mass unemployment. Before the war, despite strong efforts from President Roosevelt, unemployment in America remained at stubbornly high levels right throughout his Presidency due to the global Great Depression. It was only after America's entry into the War, after the Japanese attack on Pearl...
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