On August 6th 1945 US president Harry Truman addressed the American people, telling them that a devastating new weapon had been detonated over the Japanese industrial city of Hiroshima:

“Sixteen hours ago, an American aeroplane dropped one bomb on Hiroshima and destroyed its usefulness to the enemy. That bomb had more power than 20,000 tons of TNT. It had more than two thousand times the blast power of the British ‘Grand Slam’, which is the largest bomb ever yet used in the history of warfare.

The Japanese began the war from the air at Pearl Harbor. They have been repaid manyfold. And the end is not yet. With this bomb we have now added a new and revolutionary increase in destruction, to supplement the growing power of our armed forces. In their present form these bombs are now in production and even more powerful forms are in development.

It is an atomic bomb. It is a harnessing of the basic power of the universe. The force from which the sun draws its power has been loosed against those who brought war to the Far East…

The United States had available a large number of scientists of distinction in the many needed areas of knowledge. It had the tremendous industrial and financial resources necessary for the project and they could be devoted to it without undue impairment of other vital war work… We now have two great plants and many lesser works devoted to the production of atomic power. Employment during peak construction numbered 125,000 and over 65,000 individuals are even now engaged in operating the plants. Many have worked there for two and a half years. Few know what they have been producing. They see great quantities of material going in and they see nothing coming out of these plants, for the physical size of the explosive charge is exceedingly small. We have spent two billion dollars on the greatest scientific gamble in history – and won…

What has been done is the greatest achievement of organised science in history. It was done under pressure and without failure.

We are now prepared to obliterate more rapidly and completely every productive enterprise the Japanese have above ground in any city. We shall destroy their docks, their factories, and their communications. Let there be no mistake; we shall completely destroy Japan’s power to make war.

It was to spare the Japanese people from utter destruction that the ultimatum of July 26th was issued at Potsdam. Their leaders promptly rejected that ultimatum. If they do not now accept our terms they may expect a rain of ruin from the air, the like of which has never been seen on this earth. Behind this air attack will follow sea and land forces in such number that and power as they have not yet seen, and with the fighting skill of which they are already well aware…

The fact that we can release atomic energy ushers in a new era in man’s understanding of nature’s forces. Atomic energy may in the future supplement the power that now comes from coal, oil, and falling water, but at present, it cannot be produced on a basis to compete with them commercially. Before that comes there must be a long period of intensive research…

I shall recommend that the Congress of the United States consider promptly the establishment of an appropriate commission to control the production and use of atomic power within the United States. I shall give further consideration and make further recommendations to the Congress as to how atomic power can become a powerful and forceful influence towards the maintenance of world peace.”