During the Great Depression of the 1930's, says Wikipedia, the military leaders of Japan were able to gain the political leadership of the country.
The generals took over part of China, Southeast Asia and numerous Pacific islands.
They attacked the US fleet in Hawaii - Pearl harbor - in 1941.
In 1945 US and Australian forces were clearly winning the war but the Japanese leadership refused to surrender.
The US used their newest long-range bomber, the B-29, to pummel Japan. The firebombing of Tokyo in March, 1945, destroyed the capital and killed some 100,000 people. A million people were left homeless.
The Japanese military refused to negotiate.
In August, 1945, the atomic bombs were dropped on Hiroshima and Nagasaki. These attacks resulted in Japanese surrender.