The Potsdam Conference: July 21st 1945 – The Polish Question

At 3:30pm, Secretary of War Henry Stimson arrived at the ‘Little White House’ with a full description of the test of the atomic bomb that had taken place five days earlier on July 16th. It was sent to Babelsberg by U.S. Army Brigadier General Leslie Groves, who was overseeing the Manhattan Project back in the United States and regularly updating Stimson on developments while he was with the President at Potsdam.

Behind closed doors in Truman’s villa, Stimson read Grove’s document out loud to the President and Secretary Byrnes. It took some time, as it was fourteen pages double-spaced.

At 530, 16 July 1945, in a remote section of the Alamogordo Air Base, New Mexico, the first full scale test was made of the implosion type atomic fission bomb. For the first time in history there was a nuclear explosion. The test was successful beyond the most optimistic expectations of anyone. Based on the data which it has been possible to work up to date, I estimate the energy generated to be in excess of the equivalent of 15,000 to 20,000 tons of TNT.

Grove’s description would go on to note that windows were shattered by the blast as far off as 125 miles from ground zero. The 60 foot high steel tower, from which the bomb fell, immediately evaporated. It left a crater in the New Mexico desert more than two miles wide. It knocked down men more than 10,000 yards away and the mushroom cloud, containing a huge concentration of radioactive material, could be seen from more than 200 miles away.

After reading the document, Stimson looked up at the President to see that he was “tremendously pepped up by it,” as he would record in his diary. He went on to write:

“He (Truman) said it gave him an entirely new feeling of confidence and he thanked me for having come to the Conference and being present to help him in this way.”