s. Throughout the twentieth century, most nations that have developed nuclear weapons have tested them. Testing nuclear weapons can yield information about how the weapons work, as well as how the weapons behave under various conditions and how structures behave when subjected to nuclear explosions.
1953 Nuclear testing: At the Nevada Test Site, the United States conduct their first and only nuclear artillery test.
1954 Nuclear testing: The Castle Bravo, a 15-megaton hydrogen bomb, is detonated on Bikini Atoll in the Pacific Ocean, resulting in the worst radioactive contamination ever caused by the United States.
1957 First American underground nuclear bomb test.
1961 Nuclear testing: The Soviet Union detonates the hydrogen bomb Tsar Bomba over Novaya Zemlya; at 58 megatons of yield, it is still the largest explosive device ever detonated, nuclear or otherwise.
1964 Cold War: Indian Prime Minister Jawaharlal Nehru appeals to the United States and the Soviet Union to end nuclear testing and to start nuclear disarmament, stating that such an action would "save humanity from the ultimate disaster".
1998 India carries out two nuclear tests at Pokhran, following the three conducted on May 11. The United States and Japan impose economic sanctions on India.
1998 Nuclear testing: Pakistan responds to a series of nuclear tests by India with five of its own, prompting the United States, Japan, and other nations to impose economic sanctions.