March 5 - Non-Proliferation Treaty enters into force; 100 nations ratify it by 1980. August 19 - U.S. deploys the first missile with multiple independently targetable reentry vehicles (MIRVs).
1971
March 30 - The first Poseidon submarine-launched ballistic missiles are introduced by the U.S.
1972
May 26 - President Nixon and General Secretary Brezhnev sign the Anti-Ballistic Missile (ABM) Treaty, the Strategic Arms Limitation Treaty (SALT) and the Interim Agreement on Strategic Offensive Arms, in Moscow. November - SALT II treaty negotiations begin.
1974
May 18 - India sets off a low-yield device (8 kilotons) under Rajasthan desert. July 3 - The Threshold Test Ban Treaty (TTBT) is signed in Moscow. It limits nuclear test explosions to under 150 kilotons. November 24 - President Ford and General Secretary Brezhnev sign the Vladivostok Accord, agreeing to limit the number of strategic launchers (2400) and MIRV launchers (1320).
1976
March 31 - Threshold Test Ban Treaty enters into force. May 28 - President Gerald Ford and General Secretary Leonid Brezhnev sign the Underground Nuclear Explosions for Peaceful Purposes (PNE) Treaty.
1977
July 7 - United States successfully tests a neutron bomb. The primary lethal effects of a neutron bomb, also known as an enhanced-radiation weapon, come from the radiation damage caused by the neutrons it emits.
1978
April 7 - United States cancels development of the Enhanced Radiation Weapon or neutron bomb.
1979
March 28 - Three Mile Island Nuclear Power plant near Harrisburg, Pennsylvania, suffers a partial-core meltdown. Minimal radioactive material is released. June 18 - SALT II Treaty is signed in Vienna, Austria, by Brezhnev and President Carter. September 22 - A mysterious flash detected by a U.S. VELA satellite (that were deployed in support of the Limited Test Ban Treaty of 1963) is determined to be from a clandestine nuclear explosion. Originally, the Carter administration claims that the event was not the result of a nuclear test. However, it was revealed in 1993 that this event is from a South African nuclear test. December 26 - U.S.S.R. invades Afghanistan; SALT II Treaty removed from consideration from the U.S. Senate.