Why was the u. s. finally able to gain the upper hand on japan as losses mounted up? american forces were better prepared. america was able to rebuild faster. japan had less-capable leaders. the japanese mainland was attacked.

America was able to rebuild faster.

America's population size, economic strength and industrial powers allowed the US to not only build up her armies, but also supply allies through the lend-lease act. In fact, with all the population & natural resources the US owned, they were able to build almost as fast as their equipment being destroyed, hence a quote of "Once a .. .[tank in this instance] was destroyed, it was pushed out of the way, and replaced at once..."

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voter turnout, 2006-2012