Treaty Name: Treaty Between the United States of America and the Union of Soviet Socialist Republics on the Reduction and Limitation of Strategic Offensive Arms (START Treaty)

Signed by the United States: July 31, 1991
Ratified by the Senate: October 1, 1992
Entry Into Force: December 5, 1994

Background: START negotiations began in 1982 when the United States proposed large reductions in the nuclear arsenals of both sides. Following Soviet suspension of the negotiations, the Parties returned to the table in 1985. After exchanging proposals for the format of the START Treaty, U.S. President Regan and Soviet General Secretary Gorbachev agreed upon several specific limitations that the Treaty would enforce. They settled on, inter alia, a limit of 1,600 Strategic Nuclear Delivery Vehicles (SNDVs), and a ceiling of 6,000 warheads on the SNDVs. The Parties exchanged draft texts of the Treaty in 1987, and the agreement took shape over the next four years. The START Treaty was signed by President Bush and Secretary Gorbachev on July 31, 1991.

Treaty Structure: The Treaty consists of 19 articles; 38 agreed statements; seven protocols; numerous associated documents (such as letters and other correspondence); 47 Joint Compliance and Inspection Commission (JCIC) agreements; 36 joint statements; 19 'S' series joint statements; a definitions annex; and annexes to the Inspection Protocol and MOU.

Treaty Objectives: The START Treaty calls for reductions in the strategic nuclear arsenals of the Parties such that, no later than 84 months after entry into force of the Treaty, each Party's strategic offensive arms (SOA) do not exceed: 1,600 for deployed ICBMs, SLBMs, and heavy bombers (including a limit of 154 on deployed heavy ICBMs); 6,000 for warheads attributed to deployed ICBMs, SLBMs, and heavy bombers, including: 4,900 for warheads attributed to deployed ICBMs and SLBMs, 1100 for warheads attributed to deployed ICBMs on mobile launchers on ICBMS, and 1540 for warheads attributed to deployed heavy ICBMs. The Treaty also requires each Party to limit the aggregate throw-weight of its deployed ICBMs and SLBMs so that seven years after entry into force of the Treaty and thereafter such aggregate throw-weight does not exceed 3600 metric tons.

Treaty Provisions: The START Treaty mandates Strategic Nuclear Delivery Vehicle (SNDV) reductions over a seven year period to a central limit of 1,600 deployed ICBMs, SLBMs and heavy bombers for each party. There is an additional sub-limit of no more than 154 deployed heavy ICBMs. The total number of warheads attributed to these delivery vehicles may not exceed 6,000. Within the 6,000 limit, there is a sub-limit of 4,900 warheads attributed to ICBMs and SLBMs. There are also sub-limits on heavy ICBM warheads (1,540) and mobile ICBM warheads (1,100-exclusive of silo based variants). These attributed warhead sub-limits are not in addition to, but are within, the overall limit of 6,000 attributable warheads per Party. Finally, the Treaty permits the Parties up to 3,600 MT of aggregate throw-weight attributed to deployed ICBMs and SLBMs. This means that FSU throw-weight will be reduced from START Treaty signature levels by approximately 46%. The aggregate throw-weight of the deployed US ICBM and SLBM force is already far below this ceiling.

Since START bans new types of heavy ICBMs, the only type of heavy ICBM permitted is the existing Russian SS-18. Therefore the heavy ICBM sub-limit does not apply to the US. The Soviets agreed in a side letter to eliminate 22 SS-18 launchers every year for seven years to achieve this level. In addition to these requirements other constraints on heavy ICBMs include: no downloading; no increase in launch weight or throw-weight; no mobile launchers for heavy ICBMs; ban on new types of heavy ballistic missiles. New heavy ICBM silo construction allowed, but only in exceptional cases for relocation or to replace eliminated heavy ICBM silos in extraordinary circumstances; never to exceed 154 such silos. Modernization and testing of existing heavy ICBM's can continue.

The Treaty establishes procedures for determining and defining what a Treaty accountable item is, how it counts against the Treaty's central limits and sub-limits, how it may be based and operated, and where it can be located. The Treaty establishes specific methods for converting or eliminating Treaty accountable items to meet those set limits. Additionally, the Treaty allows the Parties to test existing and future accountable systems and permits modernization of SOA subject to the provisions and obligations of the Treaty.

The START Treaty does not constrain Sea-launched cruise missiles (SLCMs). However, each side provides the other with a politically binding declaration concerning long-range nuclear SLCMs, i.e., those nuclear SLCMs whose range is over 600 kilometers. The Parties must specify, in annual declarations, the planned maximum number of these deployed nuclear SLCMs for each of the following five Treaty years. The planned maximum number will not exceed 880 long-range nuclear SLCMs. Nuclear-armed SLCMs with a range of 300-600 kilometers will be the subject of confidential annual data exchanges. The sides will not produce or deploy multiple warhead nuclear SLCMs.

The START Treaty contains elaborate rules and procedures for determining how a system counts against the 1,600 and 6,000 limits. Under the Treaty, each deployed ICBM and its associated launcher, each deployed SLBM and its associated launcher, each long range nuclear ALCM (LRNA) equipped heavy bomber and each non-LRNA heavy bomber equipped with nuclear armaments is counted against the central limit of 1,600 delivery vehicles on a one-for-one basis. However, how the warheads attributed to each type of deployed ICBM, SLBM or heavy bomber are counted against the 6,000 attributed warhead limit depends upon its particular "warhead attribution number." The Parties agreed to the warhead attribution for ballistic missile types existing at the time of Treaty signature. For example, each deployed US Peacekeeper ICBM will count as 10 warheads against the 6,000 attributed warhead numerical limit.

The Treaty also provides rules for attributing warheads to "new types." An ICBM or SLBM will be considered a new type of ICBM or SLBM if it meets any of the following criteria: change in number of stages; change in type of propellant; 10 percent change in missile or first stage length; 10 percent change in missile launch weight; 5 percent change in diameter; 5 percent change in first stage length combined with 21 percent increase in throw-weight. Warhead attribution for future types of ICBMs and SLBMs will be the maximum number of RVs with which it has been flight-tested, but no less than the nearest integer that is smaller than the result of dividing 40 percent of the missile throw-weight by the weight of the lightest RV flight-tested on that type of ICBM or SLBM. The Parties would discuss application of the 40 percent rule to new systems with unconventional front sections within the JCIC. Additionally, there is a Ceiling of 21 percent on permitted increases to throw-weight of existing types of ICBMs or SLBMs.

The Treaty permits each side to reduce, or "down-load," the attribution number of up to three types of ICBMs or SLBMs up to an aggregate of 1250 warheads. The SS-N-18 warhead attribution was reduced to 3, therefore, a total of 896 SS-N-18 warheads count toward the downloading limit. The United States may also reduce the US Minuteman III attribution by 1 or 2 warheads. Insofar as permitted by the aggregate limit, up to 500 warheads may be downloaded on two other existing ballistic missile types (up to 4 warheads per missile). There is a ban on downloading of new types and on deploying a new type with more warheads than on a downloaded type (except for the Minuteman III and the SS-N-18). If a Party downloads an ICBM by more than two warheads, it must equip that ICBM with a new reentry vehicle platform, and destroy all the old platforms. Additionally, the Treaty prohibits the Parties from producing, flight-testing, or deploying an ICBM or SLBM with more than ten reentry vehicles or with a number of re-entry vehicles greater than the number of warheads attributed to that type of missile.

Heavy bombers are subject to favorable attributed-warhead counting rules under the Treaty-known as "discount rules." START attributes one warhead to each non-LRNA nuclear equipped heavy bomber regardless of the number of nuclear weapons it actually carries. The B-1B, therefore, would count as 1 warhead against the 6,000 ceiling even if it carried 16 gravity bombs. For LRNA-equipped heavy bombers, the first 150 so-equipped US heavy bombers each count as 10 attributed warheads against the 6,000 attributed warhead ceiling, although they may each carry up to 20 LRNA. The Treaty attributes Heavy bombers above the 150 threshold with the maximum number of warheads that any heavy bomber of the same type and variant is actually equipped to carry (12 for B-52G, 20 for B-52H). The Treaty limits the United States to a maximum of 20 LRNA on any existing or future heavy bomber. Additionally, the Treaty bans LRNAs equipped with more than one warhead.

The Parties must eliminate or convert their Treaty accountable systems in accordance with the specific procedures in the Protocol on Conversions or Elimination to meet the Treaty's numerical reduction requirements. This Protocol specifies activities a Party must initiate and/or complete to remove an item from counting against the 1,600/6,000 limit. The Treaty specifies in the Conversion or Elimination Protocol; that for SLBM launchers, elimination requires either removal of all launch tube hatches, support rings and superstructure fairings or removal of the entire missile bay section from the SSBN. The Treaty specifies that this process must occur in situ. After elimination of their launchers, silo-based ICBMs become accountable non-deployed missiles that are not subject to further numerical limits or specific elimination procedures. Verification of the numbers of SLBM and silo ICBM launchers is by NTM.

Deployed mobile ICBM launchers no longer count against the 1,600/6,000 limits upon removal of the ICBM from the launcher. Both non-deployed mobile ICBMs and non-deployed mobile launchers remain subject to other Treaty limits on non-deployed missiles (250) and launchers (110). Moreover, there are specific procedures for the elimination or destruction of both mobile missiles and launchers that the owning side must carry out in the presence of an inspection team of the other side if the missiles or launchers are to be removed from Treaty accountability. The United States has no deployed mobile ICBM launchers but, the Peacekeeper ICBM is treated as a mobile ICBM.

For heavy bombers, except for the B-2, elimination from counting against the 1,600/6,000 limits requires severing the tail section (to complete elimination the fuselage must also be severed). Conversion to a non-nuclear heavy bomber, training heavy bomber or former heavy bomber is subject to other specified procedures. The Treaty limits each side to 20 test heavy bombers and an aggregate total of 75 heavy bombers equipped only for non-nuclear armaments, former heavy bombers and training heavy bombers. A Party may verify the elimination through on-site inspection (OSI) either at the initiation or the completion of LRNA heavy bomber elimination. All nuclear bomber eliminations must be observable by NTM.

Information Exchange: The START Treaty requires a rather extensive flow of notifications and exchange of data regarding Treaty accountable items. A variety of information is required to be provided to include the following: MOU updates which are required every six months on Treaty accountable items; conversions or eliminations which are occurring throughout the year for both the US and former Soviet Union; notifications of flight tests as specified in the Treaty; new types of SOA; and inspections and data exchanges. As specified in the Treaty, the Parties transmit these notifications and data exchanges through the Nuclear Risk Reduction Centers (NRRCs).

Verification: The Treaty establishes a complex and intrusive verification regime to help verify compliance, permitting OSI, production monitoring, notification, data exchanges and cooperative measures to enhance National Technical Means (NTM) of verification. The Parties designed the basic structure of the Treaty to facilitate verification by NTM. The START Treaty contains detailed, interlocking and mutually reinforcing provisions, which supplement NTM to establish an effective verification regime. START provides for the use of, and non-interference with, NTM, e.g., satellites. There are explicit provisions prohibiting interference with NTM, or use of concealment measures that impede verification by NTM.

There are twelve types of OSI and exhibitions. These are: baseline data inspections, data update inspections, new facility inspections, suspect site inspections, reentry vehicle inspections, post-exercise dispersal inspections, conversion or elimination inspections, close-out inspections, formerly declared facility inspections, technical characteristics exhibitions, distinguishability exhibitions and heavy bomber baseline exhibitions.

START establishes continuous monitoring at the perimeter and portals of each side's mobile ICBM assembly facilities. The US has established a monitoring facility at Votkinsk, which is the final assembly facility for the SS-25. The Soviet side has the right to monitor the Thiokol Strategic Operations facility at Promontory, Utah, the final assembly facility for the accountable stage of the Peacekeeper, but has not chosen to do so. Each side has the right to establish such monitoring at any future facilities at which mobile ICBM assembly takes place.

Compliance: Compliance concerns may be raised by either side in the Joint Compliance and Inspection Commission (JCIC) or any other appropriate forum.

TC Home | Treaties & Agreements | Guidance & Directives | Training Courses | Links | E-mail the Webmaster