The Decision

Alamogordo test

The key decisions of 1945

21 July: President Truman received the report which confirmed that the Alamogordo test had been successful.

The key events around the bomb

21 JulyTruman received the report which confirmed that the Alamogordo test had been successful, and America had an atomic bomb. Truman insisted that the Japanese should be given the opportunity to surrender before the bomb was used.
26 July The British, Chinese and Americans called on Japan to surrender unconditionally. This is known as the Potsdam Declaration. The Soviet Union did not agree – the Japanese had asked them to try to negotiate a peace treaty.
28 JulyThe Japanese refused to surrender unconditionally.
3 AugustThe Japanese again asked for a negotiated peace.

Dropping the atomic bomb

6 AugustThe American B29 bomber Enola Gay dropped the first atomic bomb, codenamed 'Little Boy', on the Japanese city of Hiroshima.
  • it exploded with the force of 20,000 tons of TNT
  • the temperature at the centre of the explosion reached 3000ºC - 4000ºC – three times hotter than volcanic lava
  • everything within a mile of the centre of the blast was flattened
  • fires spread and around 67 per cent of Hiroshima's buildings were destroyed
9 AugustThe Americans dropped a second atomic bomb, codenamed 'Fat Man', on the Japanese city of Nagasaki.
14 AugustThe Japanese surrendered unconditionally.

Why did President Truman decide to drop the bomb?