In June 1945, the American president, Harry S. Truman, was faced with the unpleasant prospect of ordering an invasion of the Japanese home islands. The fierce Japanese defence of Iwo Jima (19 February-24 March 1945) and Okinawa (1 April-22 June 1945) had inflicted heavy casualties on the 3rd and 24th Marine Corps. In addition, the invasion fleet had been subjected to a series of attacks by 355 kamikazes (suicide pilots flying fighters loaded with high explosives). The kamikaze attacks destroyed 26 American ships and seriously damaged 87.
The American Joint Chiefs of Staff informed Truman that an invasion of the Japanese home islands would be very costly. On 30 July, after careful deliberation, President Truman decided to employ a new weapon, the atomic bomb, against the Japanese. The first atomic bomb had been detonated at the Alamogordo test site in New Mexico on 16 July 1945. At the same time, the United States Army Air Force (USAAF) organized the 509th Composite Group, which immediately began secretly training in Utah for atomic bombing missions.
On 6 August 1945, a USAAF B-29 bomber, the Enola Gay, dropped an atomic bomb on the Japanese city of Hiroshima. Some 78,000 Japanese were killed in the explosion and resultant fires, and a further 70,000 suffered from radiation. The USAAF dropped a second atomic bomb on Nagasaki on 9 August 1945, and 40,000 people were killed and 23,000 injured. The following day, the Japanese government requested the terms of surrender.
While Canada does not seem to have had any say in the final use of atomic bombs, it, along with Great Britain, was a full participant in the Manhattan Project (the code name for the nuclear research that developed the atomic bomb). Indeed, the creation of the bomb was the result of a tripartite American, British, and Canadian agreement. The uranium used in the weapons came from Canadian mines, and, as early as 1936, Canadian physicists at the University of Manitoba had perfected the process for producing plutonium, a fissionable isotope of uranium. Based upon this work, the Canadians and British established a large atomic research centre at Chalk River, Ontario, in 1940-1941. The Americans "invited" the Anglo-Canadian scientists to join the Manhattan Project while it was still in the planning stages. Despite the fact that the British and Canadians already had a fully equipped facility in operation, the Americans insisted that the Manhattan Project be located in the United States. They did so for security reasons. In fact, however, Soviet agents penetrated the Manhattan Project almost from the outset and were able to pass on the key details of the atomic bomb to the Soviet Union.