The most terrible thing ever discovered

The Trinity explosion, 16th July 1945
Photo: Jack Aeby

When he wrote the following diary entry on 25th July of 1945, Harry S. Truman had been U.S. President for just three months. With Nazi Germany defeated, Truman was in Potsdam, Germany with Winston Churchill and Joseph Stalin, their goal: to negotiate the end of World War II and the restructuring of Europe. As discussions rolled on, Truman became privy to a potent secret. On 16th July, in New Mexico’s Jornada del Muerto desert, the world’s first atomic bomb, a test codenamed “Trinity,” had been successfully detonated, its potential for destruction beyond anything previously imagined—an historic development that left Truman with the biggest decision he would ever have to make. A day after this entry was written, the Potsdam attendees called upon Japan to surrender or face “prompt and utter destruction.” They refused. On 6th August, the first of two atomic bombs was dropped on Japan.

The Diary Entry
Image: Harry S. Truman Library

July 25 1945

We met at 11 A.M. today. That is Stalin, Churchill and the U.S. president. But I had a most important session with Lord Mountbatten and General Marshall before that. We have discovered the most terrible bomb in the history of the world. It may be the fire destruction prophesied in the Euphrates Valley era, after Noah and his fabulous ark.

Anyway we think we have found the way to cause a disintegration of the atom. An experiment in the New Mexico desert was startling – to put it mildly. Thirteen pounds of the explosive caused a crater 6 feet deep and 1200 feet in diameter, knocked over a steel tower ½ mile away, and knocked men down 10,000 yards away. The explosion was visible for more than 200 miles and audible for 40 miles and more.

This weapon is to be used against Japan between now and August 10th. I have told the secretary of war, Mr Stimson, to use it so that military objectives and soldiers and sailors are the target and not women and children. Even if Japs are savages, ruthless, merciless and fanatic, we as the leader of the world for the common welfare cannot drop this terrible bomb on the old capital or the new.

He and I are in accord. The target will be a purely military one and we will issue a warning statement asking the Japs to surrender and save lives. I’m sure they will not do that, but we will have given them the chance. It is certainly a good thing for the world that Hitler’s crowd or Stalin’s did not discover this atomic bomb. It seems to be the most terrible thing ever discovered, but it can be made the most useful.

Further Reading

Harry S. Truman’s handwritten “Potsdam diary” is held at the Harry S. Truman. Library where it lived, hidden from public view, until 1978. In 1980 its entries were reprinted alongside Truman’s letters and memoranda in the excellent book, Off the Record: The Private Papers of Harry S. Truman.


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