Don’t Kill the Nuclear Cruise Missile

Critics of the Long Range Standoff Weapon have seized on a recent Congressional Budget Office report that says stripping the nuclear triad of current and proposed air-launched cruise missiles, or ALCMs, would save some $30 billion over three decades. But the office’s analysis discounts how this would undermine military capability and incur substantial risk.

For example, CBO concludes that the United States can eliminate the ALCM without shrinking its arsenal of survivable nuclear weapons — the ones that an enemy cannot be sure of destroying, and which therefore help deter large-scale nuclear attack. If CBO is right about the ALCM, giving it up would have no impact on stability with Russia.

Unfortunately, CBO is wrong. It arrived at this conclusion because it relied on the New START Treaty counting rule, which counts each deployed nuclear-capable bomber as a single deployed nuclear warhead. In other words, the nuclear gravity bombs and cruise missiles the United States and Russia can load onto their bombers are not counted against the treaty limit of 1,550 deployed nuclear warheads.

This rule is perfectly fine for the purpose of arms control. Both countries know that each deployed bomber can carry more than one nuclear weapon. But using the counting rule to assess the military implications of eliminating the ALCM is deeply misleading.

The United States can, in theory, arm its 41 nuclear-capable B-52H bombers with 20 cruise missiles apiece, for a total of 820 warheads. To be clear, the real number might be smaller, depending on the actual size of the cruise missile inventory, but it would still range in the hundreds.

Why does this matter? Bombers are difficult for an adversary to destroy in a nuclear attack because they can disperse and conduct airborne alerts. The ability to put hundreds of survivable nuclear weapons on U.S. bombers improves stability. On the other hand, unilaterally eliminating these survivable weapons would create a dangerous disparity with Russia, which can arm its bombers with as many as 600 nuclear ALCMs. In a crisis, this mismatch could provide Russia with coercive leverage and undermine strategic stability. CBO’s analysis does not reflect this risk.  

The United States could partially regain some of the survivable nuclear weapons it would lose by putting additional warheads on its submarine-launched ballistic missiles. (Doing the same to America’s ICBMs would not enhance survivability because silo-based missiles are not as survivable as mobile bombers and submarines.)

Unfortunately, every warhead on a submarine counts against the New START treaty limit of 1,550 deployed weapons. The United States would essentially shift survivable systems from “discounted” ALCMs to treaty-accountable SLBM warheads. Thus, in order to truly regain survivable warheads under the treaty, the United States would need to make proportionate reductions to its ICBMs. Alternatively, it could withdraw from the treaty — at the cost of scrapping an important tool for managing the nuclear relationship with Russia.

Read more: Russia Has Deployed a Treaty-Violating Missile. Here’s What the US Should Do About It

The CBO report also concluded that eliminating the ALCM would not reduce the United States’ low-yield nuclear options, apparently because bombers and tactical aircraft could still drop gravity bombs. Effective low-yield options are central to U.S. strategy for deterring an adversary from limited nuclear escalation in conventional conflicts. Unfortunately, here too the CBO’s conclusion is wrong, both quantitatively and qualitatively.

The United States cannot offset the ALCM’s low-yield contribution, provided by the W-80 warhead, by putting more warheads on its ICBMs and sub-launched missiles. As currently configured, U.S. ballistic missiles carry warheads that do not provide low-yield options. Thus, the United States would lose hundreds of low-yield nuclear weapons.

Eliminating U.S. bombers’ ability to deliver nuclear weapons from standoff range would also decrease the effectiveness of U.S. low-yield nuclear options. The gravity bomb and the cruise missile are fundamentally different weapons. Put simply, ALCMs are more effective. To deliver gravity bombs against a set of targets, a bomber must fly to each one, sequentially. In contrast, the ALCM allows a bomber to hold multiple targets at risk over a vast geographic area. Even the CBO report notes that “Cruise missiles are more difficult for air defenses to detect and track than bombers.” But for some reason, CBO’s analysis did not translate the loss of the cruise missile into an overall decrease in low-yield capability.

There are also longer-term risks to eliminating the ALCM. U.S. nuclear forces do not fulfill their deterrence role in a vacuum. We must assess their attributes relative not only to the strategic forces that potential adversaries field today, but also the forces they might possess in the future. And the United States must hedge its strategic posture against geopolitical and technological changes.

There might not be a replacement arms control treaty when New Start expires in 2021 or 2026, at which point there will be no binding constraints on Russia’s nuclear forces. Possessing a significant number of survivable ALMCs to upload if Russia attempts to escape approximate nuclear parity would be valuable. New technologies might make it easier to locate submarines, in which case mobile bombers armed with up to 20 ACLMs would help sustain the survivability of U.S. nuclear forces. Similarly, if air-defense advances make it impossible to deliver gravity bombs, the ALCMs standoff range would sustain the effectiveness of U.S. low-yield options.

These examples demonstrate how the ALCM contributes to the resiliency of U.S. nuclear forces across a range of plausible futures. Policymakers and analysts need to weigh this valuable attribute against saving $28 to 30 billion over thirty years.