On this day in 1945, President Harry S. Truman nonchalantly hints to Soviet Premier Joseph Stalin that the United States has successfully developed a new weapon. In his diary, Truman privately referred to the new weapon, the atomic bomb, as the most terrible bomb in the history of the world.
The United States had successfully tested the world's first atomic weapon near Alamogordo, New Mexico, on July 16, 1945. Truman received the news while in Potsdam, Germany, conferring with British Prime Minister Winston Churchill and Soviet leader Joseph Stalin on post-World War II policy in Europe. On July 17, Truman told Churchill of the test's success and the two agreed to put off telling Stalin about what Truman called the dynamite news until later--Truman first wanted to get Stalin to agree to enter the Pacific war on the Allies' side with no strings on it.
On July 25, after receiving Stalin's pledge to join the U.S. in the war against Japan in the Pacific, Truman casually informed the Soviet leader that the United States had a new weapon of unusual destructive force. Although Stalin did not appear to be impressed by the news, Truman hoped the information would increase the pressure on Stalin to concede to the Allies' demands regarding the post-war division of Europe.
In his diary entry for July 25, Truman wrote that the new weapon would be used against military targets in Japan before August 10. He specifically mentioned avoiding women and children and mused it is certainly a good thing for the world that Hitler's crowd or Stalin's did not discover this atomic bomb.
It turned out that Truman would not need the Soviets' help in the Pacific after all. On August 6, 1945, one week before the Soviets were due to join combat operations, Truman ordered the first atomic bomb dropped on Hiroshima, Japan. Two days later, he authorized a second atomic bomb dropped on Nagasaki. Although the total number of victims has been disputed, Japanese and U.S. government statisticians estimate that at least 140,000 men, women and children died immediately in the two blasts and an additional 74,000 died from the effects of bomb-related radiation by 1950.