July 16, 1945: The United States explodes the first atomic bomb at Alamagordo in the deserts of New Mexico. Known as the "Trinity" test, it confirms the power of the H-bombs which are dropped on Hiroshima and Nagasaki three weeks later.

1949: The Soviet Union joins the nuclear club by exploding its first atomic weapon. So begins the nuclear arms race between the US and the USSR.

1952: Britain gets on the nuclear wagon by detonating a device in the atmosphere over Christmas Island in the Pacific. Many British servicemen who were present say they were not given protective suits and claim their health has been affected by radioactivity.

1954: The United States conducts the "Bravo" nuclear test off the Marshall Islands in the Pacific. Fallout from the 15 megaton explosion affects Japan and the US later pays $15m in compensation.

1957: The US conducts the first underground nuclear tests in a mountain tunnel 100 miles from Las Vegas.

1960: France becomes an atomic power by carrying out tests in the Pacific's Tuamotu Archipelago.

India is the sixth country to have carried out a nuclear test

1962: The year of the Cuban missile crisis sees the largest number of nuclear tests, almost 200. The US and the USSR account for 95%.

1963: The US and the Soviets sign the Limited Test Ban Treaty which imposes a moratorium on underwater and atmospheric tests. Nearly 100 countries have since signed the treaty.

1964: Chairman Mao gives the go ahead for China to explode its first atomic weapon in the Lop Nor desert in Sinkiang province.

January 1966: Two US planes carrying nuclear weapons collide over Palomares, Spain. The accident and the subsequent settlement claims cost the US $182m.

1974: India begins underground testing.

1985: The Soviet Union announces it is ending nuclear testing.

1992: The US conducts its last nuclear test. The "Divider" test takes place in an underground bunker in the Nevada desert.

1995: France continues nuclear testing on the Pacific atoll of Mururoa despite international condemnation, especially from Australia and New Zealand.

1996: The United Nations General Assembly approves a comprehensive nuclear test ban treaty after China comes on board. Only India votes against the document.

April 1998: Britain and France ratify the test ban treaty. The US, Russia and China have signed the document but not ratified it. Neither India or Pakistan have signed it.

May 1998: India explodes five nuclear devices at Pokhran, its testing site in Rajasthan.

The future: Pakistan is thought to be on the verge of nuclear testing while Iraq, Iran, Libya and North Korea are also suspected of having a nuclear capability. Israel has around 100 nuclear arms but has never tested them.