The scientific discovery that would enable the creation of the atomic
bomb occurred on the eve of World War II (1939–45). In 1934, experiments with uranium by Italian physicist Enrico Fermi (1901–1954) led
to the discovery of nuclear fission. Scientists found that each fission of a uranium-235 nucleus releases 100 million times more energy than is released in a chemical reaction.
Most of the scientists who worked on nuclear fission experiments
were German or Italian. They fled their native countries as German dictator Adolf Hitler (1889–1945) and the Nazis began their ascent to
power. Had these men not emigrated to America, it is quite likely that
Hitler would have been the one to control the use of the atomic bomb.
In the late 1930s, scientist Albert Einstein (1879–1955) wrote a letter to President Franklin D. Roosevelt (1882–1945; served 1933–45),
encouraging a national effort for the development of an atomic bomb.
The government did not move quickly. It was not until mid-1942 that a
program, authorized by Roosevelt, began to build the bomb. The
Manhattan Project was the name given to the work by a division established within the Army Corps of Engineers. The sole purpose of this
project was to develop the atomic bomb.
The first nuclear bomb test was conducted on July 16, 1945, in New
Mexico. The test was a success, detonating a bomb as powerful as 20,000
tons of TNT explosives. Within a month, two such bombs were dropped
on Japan, killing an estimated 110,000 to 150,000 people and injuring another 200,000 or more. On August 15, six days after the second bomb was
dropped, Japan announced its surrender, bringing World War II to an end.
By 1962, two thousand nuclear weapons existed across the globe.
The Soviet Union and the United States owned 98 percent of them. By
the end of 2007, there were still 26,000 nuclear warheads in existence;
more than 95 percent belong to Russia and the United States.