Mathaten Prject

The United States, with assistance from the United Kingdom and Canada, designed and built the first atomic bombs under what was called the Manhattan Project. The project was initially started at the instigation of European refugee scientists (including Albert Einstein) and American scientists who feared that Nazi Germany would also be conducting a full-scale bomb development program (that program was later discovered to be much smaller and further behind). The project itself eventually employed over 130,000 people at its peak at over thirty institutions spread over the United States, and cost a total of nearly US$2 billion, making it one of the largest and most costly research and development programs of all time.

The first nuclear device, called "Gadget," was detonated during the "Trinity" test near Alamogordo, New Mexico on July 16, 1945. The Hiroshima and Nagasaki bombs were the second and third to be detonated and as of 2007 the only ones ever detonated in a military action. (See Weapons of Mass Destruction.)

During World War II both the Allies and Axis powers had previously pursued policies of strategic bombing and the targeting of civilian