On 13th August 1942 The Manhattan Project started under the direction of US General Groves.

The development of an atomic bomb had been a possibility for some years as scientists explored the possibilities of nuclear fission. German chemists  Otto Hahn and Fritz Strassmann  had made headway with this in 1938. By the outbreak of war in 1939 the rush to be the first side to develop atomic weapons was on.

In 1940 Britain made their research available to the USA which had huge financial resources available for a project to develop an atomic bomb. Scientists were aware of the devastating consequences of such a weapon.

From 1942 to 1946, the project was under the direction of Major General Leslie Groves of the U.S. Army Corps of Engineers. The nuclear physicist J. Robert Oppenheimer was the director of the Los Alamos Laboratory that designed the bombs. 

The Manhattan Project began modestly in 1939, but employed nearly 130,000 people at its peak and cost nearly US$2 billion (equivalent to about $24 billion in 2021). Over 90 percent of the cost was for building factories and to produce fissile material, with less than 10 percent for development and production of the weapons. Research and production took place at more than 30 sites across the United States, the United Kingdom, and Canada.

The world had changed forever.

The release of atomic power has changed everything except our way of thinking … the solution to this problem lies in the heart of mankind. If only I had known, I should have become a watchmaker. (1945) – Albert Einstein