Hint:The Japanese aggression had become relentless by the 1940s in Asia where it managed to acquire many territories. Post the Japanese attack on Pearl Harbour in December 1941, circumstances began to change as the U.S got greatly involved.
The United States entered into a two front war as it had declared war on Japan on December 8 while the Axis ally, Nazi Germany declared a war on it on December 11.
In 1940, Japan signed a Tripartite Pact with Germany and Italy, which made it a part of a military alliance called the ‘Axis.’ To bring about the withdrawal Japanese forces from Manchuria and China, the United States imposed various economic sanctions on Japan. By this time, Japan had begun to face severe shortages of resources including oil and desired to eradicate dominance of the United States from the Pacific region. Hence, it chose to attack Pearl Harbour. This stopped military interference by the latter for a while and Japan was able to successfully conquer Wake Island, Hong Kong, Philippines, the Dutch East Indies (Indonesia), Malaya, Singapore, and Burma. They also invaded a neutral Thailand and pressurized them to declare a war on the U.S.
American naval victory in the Battle of Midway in June 1942 made the Japanese retreat considerably. In 1944, Americans were able to recapture the Philippines and launched a strategic bombing campaign against Japan which made them even more reluctant to surrender and fleet away.
Suicidal Japanese air attacks, known as Kamikaze attacks couldn’t stop the American conquest of Okinawa in 1945.
In August 1945, the United States Army Air Force dropped atomic bombs on Japanese cities of Hiroshima and Nagasaki. Then, the USSR occupied Japan invaded Manchuria.
Ultimately, on September 2, 1945, Japan formally surrendered to the United States, Great Britain, and the Soviet Union.
Note:It is estimated that the bombing by the U.S killed 140,000 people in Hiroshima, and a further 74,000 in Nagasaki. Many survivors continue to face the brunt of diseases such as leukemia, cancer, or other adverse side effects from the radiation. In Hiroshima, 90 percent of health workers were killed, which rendered it almost impossible to treat so many people.