Hirohito was the Emporer of Japan from 1926 to 1989. In 1937, Japanese troops committed the war crime that is now known as the Rape of Nanking (the then Capital of China, now known as Nanjing). The duration of the massacre is not clearly defined, although the violence lasted well into the next six weeks, until early February 1938. During the occupation of Nanjing, the Japanese army committed numerous atrocities, such as rape, looting, arson and the execution of prisoners of war and civilians. A large number of women and children were also killed, as rape and murder became more widespread. The death toll is generally considered to be between 150,000 and 300,000. The Wikipedia article contains images and descriptions of the atrocities committed.
In his memoirs, Truman wrote that he told Stalin that the United States had “a new weapon of unusual destructive force.” Apparently, the President did not tell Stalin the new weapon was an atomic bomb, and the Soviet leader did not ask or show any special interest. He merely nodded and said something. “All he said was that he was glad to hear it and hoped we would make good use of it against the Japanese,” Truman wrote. Across the room, I watched Stalin’s face carefully as the President broke the news. So offhand was Stalin’s response that there was some question in my mind whether the President’s message had got through. I should have known better than to underrate the dictator. Years later, Marshal Georgi K. Zhukov, in his memoirs, disclosed that that night Stalin ordered a telegram sent to those working on the atomic bomb in Russia to hurry with the job.