In this lecture professor David Painter discusses the dropping of the atomic bomb on Hiroshima and Nagasaki in August of 1945 during World War II. Professor Painter establishes how the groundwork for nuclear warfare was established by President Franklin Roosevelt. He then provides reasons why the new President Harry Truman decided to use nuclear weapons against Japan, and provides some criticisms that have been brought forward since then which argue that dropping the atomic bomb was not necessary and was not for the purpose of winning the war against Japan. In the aftermath of dropping the bomb, professor Painter shows how it created the origins of what would come to be known as the Cold War between the United States and the Soviet Union.