1945 Nuclear testing: The Trinity Test, the first test of an atomic bomb, using 6 kilograms of plutonium, succeeds in detonating, unleashing an explosion equivalent to that of 19 kilotons of TNT.
1945 World War II: the Atomic bombing of Hiroshima. The United States detonates an atomic bomb nicknamed "Little Boy" on Hiroshima, Japan at 8:16 AM (local time).
1945 President Harry Truman announces the successful bombing of Hiroshima with an atomic bomb while returning from the Potsdam Conference aboard the heavy cruiser USS Augusta (CA-31) in the middle of the Atlantic Ocean.
1953 Cold War: US President Dwight D. Eisenhower formally approves the top secret document National Security Council Paper No. 162/2, which states that the United States' arsenal of nuclear weapons must be maintained and expanded to counter the communist threat.
1954 USSR tests nuclear weapon
1962 Cuban Missile Crisis begins: A U-2 flight over Cuba takes photos of Soviet nuclear weapons being installed. A stand-off then ensues the next day between the United States and the Soviet Union, putting the entire world under threat of a nuclear war.
1964 President Lyndon Johnson in New York and Soviet Premier Nikita Khrushchev in Moscow announce simultaneously plans to cut back production of materials for making nuclear weapons.
1971 The US, UK, USSR and others sign the Seabed Treaty, outlawing nuclear weapons on the ocean floor.
1974 Nuclear test: Under project Smiling Buddha, India successfully detonates its first nuclear weapon, becoming the sixth nation to do so.
1982 A rally against nuclear weapons draws 75,000 to New York City's Central Park. Jackson Browne, James Taylor, Bruce Springsteen, and Linda Ronstadt attend.
1992 Boris Yeltsin announces that Russia will stop targeting United States cities with nuclear weapons.
1994 Cold War: Russia and the People's Republic of China agree to de-target their nuclear weapons against each other.
2005 North Korea announces that it possesses nuclear weapons as a protection against the hostility it feels from the United States.