That topic would take a lifetime to explain. An Austrian by the name of Hitler decided that he should rule the world, & those with Germanic blood (Aryans) were better than all others & they should rule for a 1000 years. Meanwhile the Japanese had been attacking and just destroying all of the eastern countries, they too wanted to rule the world but first they needed raw materials in order to wage war. The US said hey that's wrong stop, & we blockaded the Japanese fleet, & cut of their supplies and $. Japan said piss off & attacked us at Pearl harbor getting the US into WWII. Germany, Italy, & a few smaller countries were allied to Japan, so they too declared war on the US & for 5 more years the world was at war.