On August 6, 1945, the United States used a massive, atomic weapon against Hiroshima, Japan. This atomic bomb, the equivalent of 20,000 tons of TNT, flattened the city, killing tens of thousands of civilians. While Japan was still trying to comprehend this devastation three days later, the United States struck again, this time, on Nagasaki. The atomic bombings of the cities of Hiroshima and Nagasaki in Japan were conducted by the United States during the final stages of World War II. To date the two bombings are the only instance of the use of nuclear weapons in wartime.
The Manhattan Project
The Manhattan Project was a research and development project that produced the first atomic bombs during World War II. It was led by the United States with the support of the United Kingdom and Canada.