The Atomic Bomb There has been a long standing debate on why the atomic bomb was used to defeat Japan. The threat of Russian advancement in Europe and in Asia was enough to worry the top officials in the United States and British governments. Wherever the Russians moved through they took for themselves. The imminent invasion of mainland Japan and the allied casualties that came with it were also a factor in the decision to drop the bomb, as said in document A. The dropping of the bomb was not entirely used to stop the Russian advancement. If the allied forces had invaded mainland Japan, many lives on both sides would have bee