The main causes for the bombings on Hiroshima and Nagasaki was because of Japan’s decision to attack the U.S at Pearl Harbor. Then following that attack they invaded the Philippines which was under the United States control at the time. The purpose of the bombs was to essentially shorten the war and to reduce the number of americans that could have been killed.
This happened in the two cities of Hiroshima and Nagasaki. On August 6, 1945 the united states bombed the city of Hiroshima, three days following the Hiroshima bombing the United states dropped a bigger bomb on Nagasaki in total the United States killed approximately 226,000 people.
The United States committed the genocide against the the Japanese.