With the invasion of Japan imminent, Truman approved the schedule for dropping the two available bombs. Truman always said attacking Japan with atomic bombs saved many lives on both sides; military estimates for the invasion of Japan were that it could take a year and result in 250,000 to 500,000 Allied casualties. Hiroshima was bombed on August 6, and Nagasaki three days later, leaving 105,000 dead.[138] The Soviet Union declared war on Japan on August 9 and invaded Manchuria. Japan agreed to surrender the following day.[139][140]

Truman announces Japan's surrender, August 14, 1945.
Supporters[f] of Truman's decision argue that, given the tenacious Japanese defense of the outlying islands, the bombings saved hundreds of thousands of lives of Allied prisoners, Japanese civilians, and combatants on both sides that would have been lost in an invasion of Japan. Critics have argued that the use of nuclear weapons was unnecessary, given that conventional attacks or a demonstrative bombing of an uninhabited area might have forced Japan's surrender and therefore assert that the attack constituted a crime of war.