Nuclear weapon bomb works by initiating a nuclear chain reaction, which releases a huge amount of energy relative to conventional explosives. Per unit volume, an atom bomb may be millions or billions of times more powerful than TNT. The first atomic explosion occurred on 16 July 1945 at the Alamogordo Test Range in New Mexico, during a test called Trinity. It was developed during the top secret Manhattan Project, which was directed by General Leslie R. Groves of the US Army