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A Thought Experiment on the Nuclear Triad

US Navy photo by Mass Communication Specialist 1st Class James Kimber, via Wikimedia.

US Navy photo by Mass Communication Specialist 1st Class James Kimber, via Wikimedia.

By Taylor Marvin

The strategic nuclear forces of the United States and Russia are divided between what is termed a triad of nuclear-armed aircraft, ballistic missile submarines, and intercontinental ballistic missiles. As I noted earlier this week, many argue that the triad system is an expensive and redundant relic, and that one or more of its legs could be eliminated with no risk to the credibility of America’s nuclear deterrence.

The Air Force’s intercontinental ballistic missiles (ICBMs) are most often singled out as the least essential leg of the triad, for numerous reasons. The fixed locations of ICBM silos tempt an enemy to strike first in an attempt to destroy them on the ground, a destabilizing incentive towards a nuclear first strike; the threat of missiles being destroyed before they can be fired pressures decision-makers to “use them or lose them” and fire on just the warning of an imminent attack, increasing the risk of accidental war; and ICBMs encourage arms races, because the number of nuclear warheads necessary to destroy an opponent’s missiles in their hardened silos is far higher than needed to end civilization. Indeed, the entire concept of the nuclear triad is an after the fact justification of a three-branched strategic nuclear force that owes more to interservice rivalry than any sound strategic concept.

One of the most common arguments against eliminating ICBMs — or any one element of the triad — is the need to hedge against technological advancements that suddenly defang one means of delivering nuclear weapons. It is possible, triad proponents argue, that a revolution in undersea detection could make it much easier to find and destroy the Navy’s ballistic missile submarines (SSBNs). These fears are overstated. As Benjamin H. Friedman, Christopher A. Preble and Matt Fay note in their paper “The End of Overkill? Reassessing US Nuclear Weapons Policy,” despite similar warnings during the Cold War after the dissolution of the USSR the US government learned that it had over, not underestimated the Soviets’ ability to detect US submarines. This will likely hold true in the future as ballistic missile submarines — which are termed “boomers” in US service — continue to grow quieter. “Remember that hawks have been warning about future US SSBNs’ vulnerability to enemy forces since the 1960s, and it has not yet arrived,” Friedman, Preble, and Fay write. “Moreover, the effort needed to achieve such technological progress is unlikely to be instant or unknown to US intelligence.”

In any case, a sudden technological advance that makes ballistic missile submarines much less survivable is no more likely than an extremely unlikely revolution that makes iron-clad ballistic missile defense possible and negates the entire concept of ballistic missiles.

But even if boomers suddenly became much more detectable, would this fatally threaten the deterrence value of a submarine and aircraft nuclear dyad? Imagine a world where, for what ever reason, submarines do not exist (say humans of this alternative reality are literally paralyzed with innate fear of the ocean’s deep).* In this world the naval leg of the nuclear triad are “ballistic missile cruisers” armed with 24 Trident II nuclear missiles, each carrying up to a dozen independent nuclear warheads. Besides being launched from the ocean’s surface rather than underneath it, these missiles are identical to those carried by US and UK SSBNs in our world. Perhaps these cruisers are also nuclear powered, again like SSBNs (the USN has operated CGNs in the past). Strategic deterrent patrols consist of a “cruiser strike group” composed of a ballistic missile cruiser, an air-defense cruiser, and two destroyers. As ballistic missile cruisers would be more affordable than a SSBN, the US Navy fields, say, twenty of them, with two thirds at sea at any given time.

A US nuclear-powered cruiser. Via Wikimedia.

A US nuclear-powered cruiser. Via Wikimedia.

Needless to say, these surface ships would be far more vulnerable than ballistic missile submarines, and in this world America’s nuclear deterrent is less robust. Ships can be tracked from the air or space, and destroyed with anti-ship missiles or other military weapons. The vulnerability of surface ships would create the same “use it or lose it” incentive towards a destabilizing launch on warning stance as land-based ICBMs. These cruisers would also be unable to sneak close to enemy shores to reduce missile flight times, one of the key advantages — or disadvantages, from a global stability perspective — of ballistic missile submarines. Cruisers would also share one of the same trip-wire problem of SSBNs, namely that a counterforce attack on submarines at sea does not carry the same weight (and hands-tying motivation for nuclear response) as one targeting ICBMs based on US territory.**

But would a fleet of ballistic missile cruisers alone constitute a credible deterrence? While far from ideal, I think that it would be. After all, destroying this “surface” leg of a triad would require killing at least a dozen heavily defended ships scattered across the globe, all before the US realized that a coordinated attack on its nuclear forces was underway and responded in kind. After all, the difficulty of pulling this off would be roughly comparable to sinking every US supercarrier more or less simultaneously, something that no one is worried about today. Even for a future adversary armed with intercontinental-range anti-ship ballistic missiles, this would be a difficult task. Certainly one not worth betting millions of lives on.

The point is that even after a sudden revolution in undersea detection that makes US boomers much more vulnerable they would still be more survivable than the ballistic missile cruisers of this alternative world. There will always be an undersea arms race between offense and defense. But this isn’t any reason to fear that submarines will suddenly become more vulnerable, and it certainly isn’t an argument against drawing down the Air Force’s ICBMs.

*Though perhaps in a world without submarines German unrestricted submarine warfare never prompts US entry into World War I, which Germany then wins, an isolated United States is not the first to develop nuclear weapons, and our ballistic missile cruisers belong to the imperial Hochseeflotte…

**This citation specifically references a comment by Tom Nichols; the format of the blog does not allow me to permalink to it directly.

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