Throughout WWII, the US, Germany, the Soviet Union, and Japan were in an arms race for an advantage in the war through an atomic bomb. The US had developed the atomic bomb first throughout the Manhattan Project. The Manhattan Project was a secret project that FDR started after Einstein sent him a letter warning the US that Germany was developing a nuclear weapon in 1939. On July 16, 1945, the atomic bomb developed throughout the Manhattan project was successful in the test run at Alamogordo, NM. At this time, the Germans had already surrendered to the Allies, and the war with the Japanese was extremely deadly on both sides. US military strategists thought a mainland invasion would have to be necessary, but it would be extremely costly and