INTRODUCTION
At the beginning of the 20th century Albert Einstein published his theory proving that energy and matter were equivalent and could be converted from one to the other. At the same time physicists were at work on atomic theory - the nature and behaviour of the smallest particles of matter (even smaller than their predecessors had thought). The urge to find a way actually to release atomic energy was irresistible to many scientists. Across more than 3 decades the discoveries were made that led to the splitting ('fission') of the nucleus of an uranium atom and a scientists' memorandum saying that 'a moderate amount of Uranium 235 would indeed constitute an extremely efficient explosive'.

That memorandum (by physicists Otto Frisch and Rudolf Peierls, who were working in Birmingham, UK) was written in 1940, and the Second World War was under way. Work on nuclear fission was now regarded by US military chiefs solely as the means to make a new and ultra-powerful bomb. No-one could be sure how long it would take, or even if it would work. In 1941 America's secret $2bn 'Manhattan Project' was set up (in Los Alamos, New Mexico) to find out. The scientists employed on the project, some of them Jewish refugees from Nazi Germany, thought it possible that their colleagues still in Germany might be trying to do the same thing. The military believed that the answer was simple: be sure to be the first to make the bomb.

In fact the war with Germany was over before the first bomb was tested (code name 'Trinity'), on July 16, 1945, near Alamogordo. The explosion, which took place at dawn, was spectacular and terrifying. The glow could be seen for 125 miles. A press release was frantically rushed out to maintain secrecy - it said that a munitions dump had blown up (no loss of life)

The scientists were exhilarated by their success, and by the extent of the energy released; but many saw that a great danger had been released as well. Some tried to stop the bomb being put into use. Some got up a petition, urging the government not to use the bomb against Japan (unless the Japanese were given a test demonstration of its power and a chance to surrender); and to ensure that the new weapon was placed under international control. But the petition was spiked by the military (they simply designated it 'secret' and didn't allow it to be circulated).

The military authorities in America had wanted to use the bomb all along. The USA was still at war with Japan, and had not forgotten the Japanese air attack on Pearl Harbor in 1941 (which had brought the USA into the Second World War). Two other bombs had been built as well as the one for the 'Trinity' test. One of them was dropped on Hiroshima, on August 6, 1945. (The other was dropped on Nagasaki on August 9.)