On January 3, 1993, President George Bush and President Boris Yeltsin signed the Treaty Between the United States of America and the Russian Federation on Further Reduction and Limitation of Strategic Offensive Arms.

The Treaty, often called START II, codifies the Joint Understanding signed by the two Presidents at the Washington Summit on June 17,1992. When implemented, it will eliminate the most destabilizing strategic weapons -- heavy intercontinental ballistic missiles (ICBMS) and all other multiple-warhead (MIRVed) ICBMS. It will also reduce dramatically the total number of strategic nuclear weapons deployed by both countries, by two-thirds below pre-START levels.

The Treaty includes a Protocol on Elimination or Conversion concerning heavy ICBMs and heavy ICBM silos, a Protocol on Exhibition and Inspection concerning heavy bombers, and a Memorandum on Attribution.

Relationship to the START Treaty

The new Treaty builds upon the START Treaty (signed on July 31, 1991 between the United States and the Soviet Union and entered into force on December 5, 1994) but will result in far greater reductions in strategic nuclear forces. All START provisions pertain, except as explicitly modified in the new Treaty. Because of the close relationship between the two Treaties, START II could not enter into force before the START Treaty. It shall also remain in force throughout the duration of START.

Central Limits

The Treaty sets equal ceilings on the number of strategic nuclear weapons that can be deployed on either side. Ceilings will come into force in two phases: Phase One to be completed seven years after entry-into-force of the START Treaty; and Phase Two to be completed by the year 2003. Phase Two may be completed by the end of the year 2000 if the United States can help finance the elimination of strategic offensive arms in Russia.

The Treaty sets ranges for some of the central limits.

Phase One

By the end of the first phase, each side must have reduced its total deployed strategic nuclear warheads to 3,800-4,250. Those include the number of warheads on deployed ICBMs and submarine-launched ballistic missiles (SLBMS) as well as the number of warheads for which heavy bombers with nuclear missions are equipped.

Of the total 3,800-4,250 warheads, no more than 1,200 may be on deployed MIRVed ICBMS, no more than 2,160 may be on deployed SLBMS, and no more than 650 may be on deployed heavy ICBMS.

Phase Two

By the end of the second and final phase, each side must have reduced its total deployed strategic nuclear warheads to 3,000-3,500. Of those, none may be on MIRVed ICBMS, including heavy ICBMS. Thus, all MIRVed ICBMs must be eliminated from each side's deployed forces; only ICBMs carrying a single-warhead will be allowed. No more than 1,700-1,750 deployed warheads may be on SLBMS. There will be no prohibition on MIRVed SLBMS.

Comparison of START and START II Central Limits

The following chart compares the central limits set by the START Treaty and by the START II Treaty.

The Treaty allows for a reduction in the number of warheads on certain MIRVed ballistic missiles. Such "downloading" is permitted in a carefully structured fashion, modifying the rules agreed in START:

• Each side will be able to download two existing types of ballistic missiles by up to four warheads each, in addition to the U.S. Minuteman III and the Russian SS-N-18. There will be no aggregate limits on the number of warheads that can be downloaded.

• A limit of 105 ICBMs of one of those types may be downloaded by up to five warheads each. Such an ICBM may only be deployed in silos in which it was deployed at the time of START signature.

Thus, the three-warhead U.S. Minuteman III ICBM, the four-warhead Russian SS-17 ICBM and 105 of the six-warhead Russian SS-19 ICBMs will be able to be downloaded to a single warhead, to comply with the requirement to eliminate all MIRVed ICBMS. The U.S. Peacekeeper ICBM and the Russian SS-18 heavy ICBM and SS-24 ICBM, each of which carry ten warheads, and the remaining SS-19 ICBMs must all be eliminated, in accordance with START procedures.

Missile System Elimination

In START, deployed SLBMs and most deployed ICBMs may be removed from accountability either by destroying their launchers (silos for fixed ICBMS, mobile launchers for mobile ICBMS, and launcher sections of submarines for SLBMS), or by converting those launchers so that they can only carry another type of permitted missile. The one exception is the SS-18; under START, the requirement to eliminate 154 deployed SS-18s must be met through silo destruction, not conversion.

In the new Treaty, those rules generally continue to apply. The major exception is again the SS-18. Ninety SS-18 silos may be converted to contain a single-warhead missile, which Russia has said will be an SS-25-type. The Treaty lays out specific procedures, including on-site inspections, to ensure that those converted silos will never again be able to launch a heavy ICBM. The remaining 64 SS-18 silos subject to this Treaty will have to be destroyed.

In exchange for the right to retain up to 90 converted SS-18 silos, the Treaty requires that all SS-18 missiles and canisters, both deployed and non-deployed, be eliminated no later than January 1, 2003. This is a major change from the START Treaty. Generally, START did not seek destruction of missiles. But in START II, the Russians have agreed to eliminate all SS-18 n-missiles, both deployed and non-deployed. This fully achieves a long-standing U.S. goal, to eliminate complete heavy ICBMS.

Heavy Bombers

In START, nuclear heavy bombers are subject to more flexible counting rules than are ballistic missiles. Each heavy bomber equipped to carry only short-range n-missiles or gravity bombs counts as one warhead. U.S. heavy bombers equipped to carry long-range nuclear air-launched cruise missiles (ALCMs) each count as 10 warheads, and Soviet heavy bombers equipped to carry long-range nuclear ALCMs each count as eight warheads.

In START II, heavy bombers are counted using the number of nuclear weapons -- whether long-range nuclear ALCMS, short-range missiles or gravity bombs -- for which they are actually equipped. This number is specified in the Treaty Memorandum on Attribution and will be confirmed by a one-time exhibition and by routine START on-site inspections.

Another new feature of this Treaty is the provision that up to 100 heavy bombers that have never been accountable under the START Treaty as long-range-nuclear-ALCM heavy bombers may be reoriented to a conventional ]role. Such bombers will not count against the Treaty warhead limits. They will be based separately from heavy bombers equipped for nuclear weapons, will be used only for non-nuclear missions, and will have observable differences from other heavy bombers of the same type that are not reoriented to a conventional role. Such heavy bombers may be returned to a nuclear role after three months notification, but then may not be reoriented again to a conventional role.

Verification

The comprehensive START verification regime applies to the new Treaty. In addition, START II includes some new verification measures, such as observation of SS-18 silo conversion and missile elimination procedures, exhibitions and inspections of all heavy bombers to confirm weapon loads, and exhibitions of heavy bombers reoriented to a conventional role to confirm their observable differences.