Instead, SORT came into effect, reducing strategic warheads count per country to 1,700 - 2,200.
MIRVed land-based ICBMs are considered destabilizing because they tend to put a premium on striking first. A MIRVed missile is able to carry 3-12 warheads and deliver them to separate targets. Thereby, if it is used in a first strike, it possibly destroys many of the enemy's missile sites.
Hypothetically, if one were to assume that each side had 100 missiles, with 5 warheads each, and further that each side had a 95 percent chance of neutralizing the opponent's missiles in their silos by firing 2 warheads at each silo, then the side that strikes first can reduce the enemy ICBM force from 100 missiles to about 5 by firing 40 missiles with 200 warheads and keeping the remaining 60 missiles in reserve. Thus the destruction capability is greatly multiplied by MIRV, when the number of enemy silos does not significantly increase.
The historic agreement started on 17 June 1992 with the signing of a 'Joint Understanding' by the presidents. The official signing of the treaty by the presidents took place on 3 January 1993. It was ratified by the U.S. Senate on 26 January 1996 with a vote of 87-4. However, Russian ratification was stalled in the Duma for many years. It was postponed a number of times to protest American military actions in Kosovo, as well as to oppose the expansion of NATO.