Original: The atomic bombings of Hiroshima and Nagasaki were nuclear attacks near the end of World War II against the Empire of Japan by the United States at the executive order of U.S. President Harry S. Truman on August 6 and August 9 , 1945 , respectively .
Simplified: The atomic bombings of Hiroshima and Nagasaki were nuclear attacks at the end of World War II against the Empire of Japan by the United States coordinated by the U.S. President Harry S. Truman on August 6 and 9 , 1945 .