United States and Soviet Union sign the START I treaty

What was United States and Soviet Union sign the START I treaty?

START I (Strategic Arms Reduction Treaty) was a bilateral treaty between the United States and the Soviet Union on the reduction and the limitation of strategic offensive arms. The treaty was signed on 31 July 1991 and entered into force on 5 December 1994. The treaty barred its signatories from deploying more than 6,000 nuclear warheads and a total of 1,600 intercontinental ballistic missiles (ICBMs) and bombers. START negotiated the largest and most complex arms control treaty in history, and its final implementation in late 2001 resulted in the removal of about 80% of all strategic nuclear weapons then in existence.

Proposed by US president Ronald Reagan, it was renamed START I after negotiations began on START II. Following the 1991 dissolution of the Soviet Union, the Lisbon Protocol bound the successor states Russia, Belarus, Ukraine, and Kazakhstan, to the terms of START, as all four were in possession of former Soviet strategic nuclear weapons. The protocol was signed in May 1992 and effective December 1994. The treaty expired on 5 December 2009. On 8 April 2010, the replacement New START Treaty was signed in Prague by US president Barack Obama and Russian president Dmitry Medvedev.

Following its ratification by the US Senate and the Federal Assembly of Russia, the treaty went into force on 5 February 2011, extending deep reductions of American and Soviet or Russian strategic nuclear weapons through February 2026. However, on 21 February 2023, Russia suspended its participation in New START but it did not withdraw from the treaty, and clarified that it would continue to abide by the numerical limits in the treaty. On 5 February 2026, New START officially expired.