What did the United States use in the attack on Hiroshima and Nagasaki in 1945 to end the war?

The United States used the Atomic Bomb on Hiroshima and Nagasaki.

These bombs, while in research and development, were referred to as the "Manhattan Project."

On August 6, 1945, during World War II, an American B-29 bomber dropped the world's first deployed atomic bomb over the Japanese city of Hiroshima. The explosion wiped out 90 percent of the city and immediately killed 80,000 people; tens of thousands more would later die of radiation exposure.