Part 2: The Story behind the numbers: The NPT nuclear weapon states 4. The United States Nuclear Weapons and Delivery Systems At the beginning of January 2011, the United States had an estimated 2,150 operationally deployed nuclear weapons. Of these, some 1,950 were thought to be deployed on strategic delivery vehicles, of which 500 were deployed on ICBMs, 1,152 on SLBMs, and 300 on strategic bomber aircraft. In addition, the United States had an estimated 200 non-strategic nuclear weapons assigned to dual-capable (conventional and nuclear) aircraft stationed at airbases in Europe. Beyond this, and not operationally deployed, the United States holds around 2,850 warheads in reserve and a further 3,500 retired 22 warheads awaiting dismantlement. This makes for an estimated total stockpile of 8,500 nuclear weapons. Under the terms of the New Strategic Arms Reduction Treaty (START) signed with Russia, which officially entered into force with the exchange of Instruments of Ratification between Secretary of State Clinton and Foreign Minister Lavrov in Munich on 5 February 2011, the United States is committed to reducing its stockpile of operationally deployed strategic nuclear warheads from its current 1,950 to 1,550. It is also committed to a limit of 700 deployed strategic launchers (missiles) and heavy bombers, and to a combined limit of 800 deployed and non-deployed strategic launchers and heavy 23 bombers. It has until February 2018 to meet these central treaty limits on its overall force structure. The size of the U.S. deployed nuclear force, in terms of both numbers of weapons and numbers of strategic launchers, is therefore clearly reducing. However, it is important not to over-state the scale of planned reductions in the U.S. force as a result of New START.
22 All data in this paragraph is drawn from Hans M. Kristensen and Robert S. Norris, “U.S. nuclear forces, 2011,” Bulletin of the Atomic Scientists, March/April 2011, p.66 and Table 2 on p.74. 23 For more details on the Treaty’s entry into force and on the implementation requirements and timelines, see background information provided by the U.S. State Department at: http://www.state.gov/r/pa/prs/ps/2011/02/156037.htm
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The New START Treaty does not set sub-limits that constrain how the overall treaty limits on warhead and strategic launcher numbers are to be achieved. The Obama Administration has decided that to stay within the overall limits, it will maintain a force composition that consists of up to 420 ICBMs, each carrying a single warhead; 240 SLBMs, each carrying multiple warheads and deployed on a fleet of 12-14 nuclear powered 24 ballistic missile submarines (SSBNs), and around 60 heavy bombers capable of delivering either gravity bombs or cruise 25 missiles. However, the New START Treaty covers only deployed strategic nuclear warheads and deployed and non-deployed strategic launchers and delivery systems, and not sub-strategic nuclear weapons or nuclear warheads held in reserve. The significance of this can be illustrated through reference to the Obama administration’s plans for the future of the U.S. ICBM force. The decision to deploy only one warhead on each of its deployed ICBMs in future means that, in practice, ICBMs already equipped with multiple warheads will have some of those warheads removed. These warheads will not however, be destroyed. Each United States ICBM will also retain its multiple independent re-entry vehicle (MIRV) capability, meaning that in future the U.S. could rapidly upload hundreds of removed but not destroyed warheads to these missiles once again (though it would need to withdraw from the New START Treaty to do so). Similarly, under New START’s counting rules, warheads removed from SLBMs on submarines undergoing overhaul are not counted by the Treaty, even though these weapons could be re-mated with their missiles and be deployed again fairly quickly. This is not a trivial matter: At any given time, two U.S. SSBNs, each potentially carrying 96 warheads on 24 Trident II D5 SLBMs, are undergoing overhaul.
24 The U.S. currently has a total of 14 Ohio-class SSBNs, of which 12 are thought to be operational. Eight of the submarines are based in the Pacific and six in the Atlantic. The 12 operational submarines each carry up to 24 Trident II D5 SLBMs, and each missile is thought to carry four warheads. This makes up a total of 288 missiles carrying the estimated total of 1,152 warheads mentioned in the text. At any given time, two submarines are undergoing overhaul. 25 Hans M. Kristensen and Robert S. Norris, “U.S. nuclear forces, 2011,” Bulletin of the Atomic Scientists, March/April 2011, p.67. 26 Ibid, p.68.
Beyond the United Kingdom: Trends in the Other Nuclear Armed States