Reduce the Size of the Nuclear Triad

Background

The United States' nuclear deterrence strategy, developed during the Cold War, is built around the strategic nuclear triad, which comprises long-range bombers, intercontinental ballistic missiles (ICBMs), and submarines that launch ballistic missiles (SSBNs). Each component of the triad plays a particular role that complements the other two. Bombers provide flexibility, and by changing the pace or location of their operations, the United States can signal intent to an adversary. ICBMs provide the most rapid response, and their dispersed underground silos present several hundred targets that an adversary would need to destroy to disable the United States' nuclear forces. The ability of SSBNs to remain on alert while submerged and undetectable for long periods makes them the most difficult of the three components to destroy and ensures that the United States can retaliate against a nuclear attack. That ability to retaliate and assure the destruction of an adversary who launched a nuclear attack helps provide stability during a crisis by deterring adversaries from using nuclear weapons.

The most recent arms control treaty between the United States and Russia, New START, limits strategic forces to 700 deployed delivery systems and 1,550 deployed warheads. (The treaty also limits forces to 800 total deployed and nondeployed delivery systems.) To comply with those limits, which took effect in 2018, the United States maintains a nuclear force consisting of the following components: 12 deployed (14 total) Ohio class SSBNs that together carry up to 1,090 warheads on 240 missiles; 400 deployed (454 total) Minuteman III ICBMs, each carrying a single warhead; and 60 deployed (66 total) B-52H and B-2A bombers, each of which counts as a single warhead under the treaty's rules.

Almost all components of the United States' nuclear forces are scheduled to be modernized (refurbished or replaced by new systems) over the next 20 years. Current plans call for developing and purchasing 12 new SSBNs, 642 new ICBMs (of which up to 450 would be fielded in existing silos after the silos were refurbished, and the remainder would be spares and test stock), and 80 to 100 B-21 bombers, the next-generation long-range strategic bombers now under development. Through the mid-2030s, modernization is expected to nearly double the amount spent annually on nuclear forces (currently about $30 billion).

Option

This option would reduce the costs of modernization by retiring some existing delivery systems early and by purchasing fewer of the new systems. It would still allow the United States to retain the strategic benefits provided by the complementary roles of the triad's three components. The Congressional Budget Office examined two alternative approaches to reducing the size of the triad: The first would keep U.S. forces at the New START limit of 1,550 warheads, and the second would make deeper cuts and reduce the number of deployed warheads to 1,000. Neither alternative would change the size or composition of the planned bomber fleet because the number of bombers is determined largely by their conventional (that is, nonnuclear) mission.

The first alternative would reduce forces to 10 SSBNs and 300 ICBMs and would load more warheads on SSBNs or ICBMs. Under that alternative, the Navy would retire 4 Ohio class SSBNs at a rate of one per year starting in 2020; delay by one year the purchase of new SSBNs included in its current shipbuilding plan, starting with the second submarine, which is slated to be procured in 2024; and cancel orders for the last 2 SSBNs scheduled to be purchased under the current plan. In addition, the Department of Defense (DoD) would retire 150 ICBMs—50 each year for three years starting in 2020—and procure 482 new ICBMs instead of the 642 that are in the current plan.

The second alternative under this option would make deeper cuts to forces but still retain a triad structure. Under that alternative, the Navy would field 8 SSBNs, and the Air Force would deploy 150 ICBMs. That force level would be reached by retiring existing systems early, starting in 2020, and by purchasing fewer replacement systems.

Effects on the Budget

Over the next decade, the first alternative would reduce discretionary budget authority by about $11 billion compared with amounts under DoD's plan, CBO estimates. Outlays would decrease by a smaller amount—nearly $8 billion over that period—because the budget authority provided would not be spent right away since developing new systems requires extensive research and planning. The majority of savings from this alternative would occur after 2028, when DoD would purchase fewer new systems and operate fewer systems overall than it would under its current plan.

The second alternative would reduce discretionary budget authority through 2028 by about $13 billion compared with amounts under DoD's plan. Outlays would decrease by about $9 billion. As with the first alternative, the majority of savings would occur after 10 years, when DoD would purchase and operate fewer modernized systems.

Even though the second alternative would cut roughly twice as many systems as the first alternative, the savings under the second alternative would be considerably less than twice as much as under the first alternative. (For the new systems, 4 fewer submarines and 320 fewer ICBMs would be purchased in the second alternative, compared with 2 fewer submarines and 160 fewer ICBMs in the first alternative; for the existing generation of systems, 6 submarines and 300 ICBMs would be retired early in the second alternative, compared with 4 submarines and 150 ICBMs in the first alternative.) That nonlinear scaling results from two primary causes. In both alternatives, even though fewer new systems would eventually be purchased, CBO assumed those canceled purchases would come at the end of the production run, which would occur after 2028. Also, the early retirement of existing systems would occur gradually under this option. Thus, the retirements of the additional systems in the second alternative would occur later in the 10-year period, so DoD would have fewer years in which to accrue savings from forgoing operations.

CBO's estimate of the costs of this option involves some uncertainty. Historically, programs that develop new systems have often experienced costs that exceed initial estimates. Development of the new submarines and ICBMs may cost more than estimated—particularly for the ICBM, which is in the very early design stages for its new missile. Another source of uncertainty concerns the savings that would accrue from the early retirement of existing systems. CBO's estimate is based on a model in which half of the operating costs for a system are fixed, and half vary linearly with the number of systems deployed (for example, retiring 50 percent of the ICBMs would result in a savings of 25 percent in operating costs). However, actual savings from early retirements may not follow that model.

Other Effects

An argument in favor of the first alternative is that it would reduce the cost of nuclear modernization without sacrificing the complementary roles of the triad or reducing the size of nuclear forces significantly below those permitted under New START. In addition, scaling back plans now might lessen the chances of troubled programs being canceled later and thus might prevent development funding for such programs from being wasted.

An argument against the first alternative is that it would decrease the capabilities of nuclear forces. In particular, with fewer submarines the Navy might not be able to meet its current goals for the number of SSBNs on patrol, even though the number of warheads deployed with the submarine fleet could remain the same as under the current plan. In addition, cutting the number of ICBMs that were deployed by one-third would present fewer targets to an adversary, thereby increasing the likelihood that the adversary could disable that component of the United States' nuclear triad.

The arguments for and against the first alternative also apply to the second alternative. Another argument in favor of the second alternative is that a force with 1,000 warheads would continue the trend started by earlier arms control treaties, which have made the United States' current nuclear arsenal about 85 percent smaller than it was at its peak during the Cold War. Some analysts argue that further reduction would strengthen efforts at preventing nuclear proliferation by continuing the United States' compliance with the Nuclear Non-Proliferation Treaty, in which countries with nuclear weapons agreed to work toward reducing and eventually eliminating such weapons and, in exchange, countries without nuclear weapons agreed to not develop or acquire them. Moreover, proponents would argue, a smaller force would still be sufficient for deterrence: The official Nuclear Weapons Employment Strategy of the United States, released in 2013, states that the United States could maintain a "strong and credible" strategic nuclear deterrent with about one-third fewer weapons deployed than the number allowed under New START.

An argument against the second alternative is that reducing U.S. nuclear forces in the current geopolitical environment could spark new arms races and might increase the chances that an adversary would launch a nuclear attack on the United States. For example, the most recent Nuclear Posture Review, released in 2018, concludes that the geopolitical environment has deteriorated markedly since the last Nuclear Posture Review in 2010 and that the world has returned to a state of "Great Power" competition. In that international atmosphere, a new arms control agreement would have little chance of being reached, so a decision by the United States to reduce its stockpile to 1,000 warheads would be unilateral, which some analysts argue could reduce strategic stability. Internationally, allies that do not have their own nuclear weapons and thus rely on U.S. nuclear forces to deter attacks would probably oppose such cuts. If they determined that a reduction to 1,000 warheads signaled that the United States was less committed to protecting them than it has been in the past, they might choose to pursue their own nuclear weapons programs, which could provoke regional arms races. Furthermore, this alternative would diminish the capabilities of U.S. nuclear forces even more than the first alternative. The possibility of the Navy's encountering difficulties in meeting its goals for the number of SSBN patrols under this alternative would therefore be greater than under the first alternative, and the smaller ICBM force would present even fewer targets to an adversary.