4/25/1945
Secretary of War Stimson and General Groves brief President Truman on the bomb.

5/25/1945
Leo Szilard visits White House with letter of introduction from Albert Einstein to warn President Truman of the dangers that atomic weapons pose for the post-War world and to urge him not to authorize use of atomic weapons against Japan.

7/16/1945
US scientists perform first successful A-Bomb test at Alamogordo, New Mexico.

7/19/1945
Truman meets Stalin and Churchill at Potsdam and tells Stalin about the A-bomb.Truman approves General Groves’ recommendation to use the A-bomb on Japan.

8/6/1945
US drops “Little Boy” nuclear bomb on Hiroshima, immediately killing 140,000 citizens. Use of the A-Bomb in WWII - Statement by the President Announcing the Use of the A-Bomb at Hiroshima.

Little Boy

8/9/1945
US drops “Fat Man” nuclear bomb on Nagasaki, immediately killing 70,000 citizens.

Fat Man

Fat Man Mushroom Cloud

Hiroshima and Nagasaki, PBS video

11/15/1945
Truman adopts the Truman-Attlee-King declaration (New Quebec agreement). The President's News Conference following the signing of a Joint Declaration on Atomic Energy.

12/24/1945
Soviets notify the US that they are developing the A-bomb.

3/4/1946
Truman declares that all US land with fissionable material is subject to government use and ownership. (These rights are later given to the AEC in December.) Executive Order 9701

7/25/1946
US performs A-bomb test at Bikini Atoll. Statement by the President Concerning Preparations for Nuclear Tests in the Pacific.

8/1/1946
Truman signs Atomic Energy Act (Public Law 79-585/McMahon Act), creating an Atomic Energy Commission (AEC) to replace the Manhattan Engineering Distict (MED). Earlier Letter to Senator McMahon  regarding energy bill. Truman’s Reflection on Atomic Energy bill two years later.

December 1946
Truman gives Atomic Energy Commission (AEC) jurisdiction over US fissile materials and sites. Executive Order 9816

6/27/1947
Truman plans for new A-bombs. Truman’s Diary Entry.

1948
US performs A-bomb tests at Eniwetok. Truman’s letter to Secretary Forrestal on the Atomic Weapons Tests at Eniwetok.

8/29/1949
The Soviets perform their first successful A-bomb test, referring to it as “First Lightening” while the US called it Joe 1 after Stalin. Truman’s Statement to the American public.

1/31/1950
Truman announces US plans to develop the H-bomb. Audio, Representative Henry Jackson on the H-Bomb Decision.

1951
USSR explodes another A-bomb. Statement Directed by Truman Addressing Recent USSR A-Bomb Explosion.

2/28/1951
Truman establishes airspace reservation over the Las Vegas Project in Las Vegas, Nevada. This site would eventually witness around 1000 nuclear tests. (Natural Resources Defense Council, Nuclear Weapons Databook Project). Executive Order 10218

9/25/1951
Truman establishes airspace reservation over the Savannah River Plant of the US AEC.