Center for Arms Control and Non-Proliferation

Nuclear Weapons Counting Rules Under START I, the Moscow Treaty, and New START

by John Isaacs [contact information]

START COUNTING RULES

• What was counted:
-Deployed strategic delivery vehicles and accountable warheads (for example, if a Trident missile was tested with eight warheads, all Trident missiles would be counted with eight warheads whether the missile actually carried three, five or eight warheads in reality).

• Ceilings:
-1,600 delivery vehicles: deployed intercontinental ballistic missiles (ICBMs), submarine-launched ballistic missiles (SLBMs), and heavy bombers for each side.
-6,000 "accountable" warheads on ICBMs, SLBMs, and heavy bombers, of which no more than 4,900 may be on ICBMs and SLBMs, 1,540 on heavy missiles (the Soviet SS-18), and 1,100 on mobile ICBMs. The total warhead count for each side was determined by adding up the number of warheads assigned to each missile and bomber.
-Ballistic missile throw-weight (lifting power) is limited to 3,600 metric tons on each side.
-Reductions were achieved in December 2001. The treaty expired on December 5, 2009.

• Specific Limits:
-START counted each type of missile and bomber as one delivery vehicle against the limit of 1,600 delivery vehicles. Each type of missile and bomber was also assigned a specific number of warheads. The number of warheads assigned to each type of missile generally – though not always – equaled the maximum number of warheads the missile had been tested with and could carry. For example, the U.S. Trident II submarine-launched ballistic missile was assigned eight warheads, while the Russian SS-18 intercontinental ballistic missile was assigned ten warheads.
-Heavy bombers equipped only with bombs or short-range attack missiles (SRAMs) are counted as carrying one warhead each. U.S. heavy bombers could carry no more than 20 long-range air-launched cruise missiles (ALCMs) each. The first 150 of these bombers count as carrying only 10 ALCMs each. Soviet heavy bombers may carry no more than 16 ALCMs each. The first 180 of these bombers count as carrying only eight ALCMs each.
-Missiles and bombers counted for the number of warheads they were assigned regardless of how many warheads they actually carried or whether they had been converted to carry conventional (non-nuclear) warheads. They also counted until the missiles and bombers were properly eliminated according to START I’s elimination rules.
-No more than 1,250 warheads may be "downloaded" (removed from) and not counted on existing multiple-warhead ballistic missiles.

TREATY OF MOSCOW (SORT) COUNTING RULES

• What was counted
-Deployed, strategic weapons only.

• Ceilings:
-Between 1,700 and 2,200 deployed strategic warheads.
-Unlike past strategic arms control agreements between Moscow and Washington, SORT does not specify which warheads are to be reduced or how reductions should be made.

• Vague interpretation of SORT commitments:
-The U.S. counted the number of warheads on its “operationally deployed” intercontinental ballistic missiles (ICBMs) and submarine-launched ballistic missiles (SLBMs), as well as warheads loaded on heavy bombers or stationed at heavy bomber bases. Some spare strategic warheads stored at heavy bomber bases, however, are not counted against the treaty limit.
-This gave the U.S. the flexibility to reduce the number of deployed warheads by removing or “downloading” warheads from delivery vehicles and putting them in storage.
-Russia officially opposed the Bush administration’s way of counting because it gives the U.S. the ability to quickly increase or “upload” warheads from its reserve stockpile to ready-to-fire missiles. It has not publicly stated what warheads it considers limited by the treaty.

NEW START COUNTING RULES:

• What is counted:
-Deployed strategic delivery vehicles and deployed strategic warheads

• Ceilings:
-1,550 deployed strategic warheads. Warheads on deployed ICBMs and deployed SLBMs count toward this limit and each deployed heavy bomber equipped for nuclear armaments counts as one warhead toward this limit.
-Two limits on delivery vehicles:
1. A combined limit of 800 deployed and non-deployed ICBM launchers, SLBM launchers, and heavy bombers equipped for nuclear armaments.
2. A separate limit of 700 deployed ICBMs, deployed SLBMs, and deployed heavy bombers equipped for nuclear armaments.
-Reductions are to be achieved seven years after the treaty enters into force. The agreement will remain in force for a total of ten years unless superseded by a new treaty.

• Specific Limits:
-New START’s counting rules combine elements from both START and the Moscow Treaty. Like START, New START counts each type of missile and bomber as one delivery vehicle against the limits of 700 and 800 delivery vehicles. Like the U.S. interpretation of the Moscow Treaty, New START counts only those nuclear warheads that are actually deployed, save for the bomber counting rule. The new treaty largely reflects a splitting of the difference between Russia’s preferred approach of counting delivery vehicles, and the U.S.’s preferred approach of counting deployed warheads.
-Because New START limits actual deployed warheads, it includes verification and monitoring provisions, including on-site inspections, to count the actual number of missiles deployed on delivery vehicles.
-In a partial departure from how START I counted warheads, each deployed heavy bomber counts as one warhead toward this limit regardless of whether it is equipped to carry air-launched cruise missiles (ALCMs).
-New START will not count U.S. delivery systems – such as B-1 bombers and the four Trident submarines – that have been converted to conventional-only roles.
-A more definitive judgment on what delivery systems will count as deployed and non-deployed under the treaty must await the release of the final text.