On This Day…

On the 13th July 1945 the first atomic bomb arrived at its test site

On this day in 1945, the first atomic bomb arrived partly assembled at its test site in the New Mexico desert. By Sunday, it was completed and set at the top of a tower waiting for the first atomic bomb ‘Trinity’ test the next day. On Monday 16 July 1945, it was successfully exploded and the nuclear era began.


The gadget

Nicknamed the ‘gadget’, the plutonium-based implosion-type device yielded 19 kilotons, creating a crater over 300 metres wide. A mere 21 more days later, the world’s first deployed atomic bomb was dropped on Hiroshima, Japan.

Trinity was the first of over 2000 nuclear tests to be conducted worldwide, with over 1000 in the US nuclear testing programme alone. The tests released vast amounts of radioactivity around the globe. They also spurred the proliferation of nuclear weapons hundreds of times more powerful than the earliest prototypes.



The Comprehensive Nuclear-Test-Ban Treaty bans all forms of nuclear testing. The United States was the first country to sign it when it opened for signature on 24 September 1996. Today, however, it is one of the eight countries that have still to ratify the Treaty before it can enter into force. The others are China, the Democratic People’s Republic of Korea, Egypt, India, Iran, Israel and Pakistan.