Partitioning the Nuclear Oceans

During the Cold War, a nuclear-armed missile fired from a submarine would likely be known to come from either the USSR or one of the NATO allies. In a world with more than two alliances possessing nuclear-armed submarines and no limits on where they patrol, however, it could become difficult during or in the immediate aftermath of a nuclear attack to reliably identify the source of that attack. This situation could seriously undermine the rationale for nuclear deterrence, which relies on knowing where to threaten to retaliate. One approach to addressing this problem is a verifiable agreement to limit patrol regions for nuclear-armed submarines in a way that would allow excluding the possibility that a missile launch came from one or more targets for retaliation.

A warning system may be able to rapidly discriminate between a ballistic and cruise missile. Rapid discrimination between different countries’ missiles launched from the same location would have to rely on differences in flight characteristics, which would be more difficult to discern even with a detailed inspection and verification system aimed at maintaining differences sufficient to be detected in the limited available in flight times. It could thus be helpful to have confidence that a potential adversary’s submarines armed with either ballistic or cruise missiles was not patrolling in a restricted area, so that a launch from that area would not trigger immediate retaliation against that particular potential adversary.

Three approaches to zoning are considered here: exclusive patrol zones, patrol zones separated by nuclear weapons free areas, and a three-zone system. The three zone system consists of “special oceanographic zones” in waters near coasts, a larger zone beyond those waters, and a more distant nuclear weapons free zone. Only the three-zone system is discussed here, because this discussion also helps clarify how the systems with fewer zones would function.

In a special oceanographic zone, collection of information in the zone’s water or air that could substantially help reveal the location of submarines would be restricted to an adjacent country with nuclear weapons. The zone would be bounded by a “picket line” equipped with devices for detecting other countries’ submarines crossing the zone boundary. The adjacent country would conduct extensive oceanographic research aimed at building a data-informed model of the zone comprehensive enough to help build confidence that any submarine that crossed the picket line would be detected and subsequently tracked. Parties to an agreement on partitioning would refrain from military naval operations in another participating country’s special oceanographic zone. Other countries adjacent to the zone would be provided with data that could be of economic but not military value. For countries or alliances with long-range submarine-launched ballistic missiles, such zones might include the South China Sea, the Gulf of Mexico and the North Sea, one or more seas adjacent to Russia, and the Andaman Sea or part of the Bay of Bengal.

Adjacent to each country’s special oceanographic zones would be zones also reserved for patrol of the same country’s ballistic missile submarines. Military vessels armed with non-nuclear weapons would not be precluded in such an exclusive nuclear patrol zone, but there could be limits on activities aimed at detecting submarines and an agreement not to use attack submarines or surface or air assets armed with anti-submarine weapons to track and trail the nuclear-armed submarines of the country assigned to the patrol zone. These larger zones would be surrounded by internationally monitored picket lines aimed at building confidence that nuclear-armed submarines neither enter the zone nor leave the zone into nuclear-weapons-free naval zones lying in between the exclusive patrol zones.

A prerequisite for any serious consideration of negotiating nuclear naval partitioning would be thorough study of verification technologies. One likely component would be a dedicated physically tamper-proof and cyber-secure inertial navigation system (INS) that occasionally (e.g. as often as once a day for a submarine operating for a day at full speed) releases information aimed at helping to verifying that the submarine had not crossed into a nuclear weapons free zone, but not revealing enough information to substantially help in targeting the submarine for attack. The INS software would need to be secure against hacking to falsify location informing or to reveal unauthorized information about location details. The information might be sent from powered drones that have moved away from a submarine on an undisclosed path. Alternatively or additionally, signals might be transmitted by tightly focused directional signal transmissions to or through a network of relays before sending the information out for verification by another party. Picket lines could use conventional hydrophones, perhaps augmented with other technological developments (c.f. Clark 2015). Port monitoring would likely be necessary to verify both the installation and integrity of dedicated INS systems and which vessels have nuclear weapons and missiles of which type.

Studies illustrating the technological feasibility of naval nuclear weapons partitioning would be a prelude to the challenging political problem of initiating and completing negotiation of agreements on international cooperation. Likely, some countries capable of naval nuclear weapons deployments would at least initially not participate. Such countries would remain at risk of retaliation after attack by a third party whose missiles could not be discriminated from those of the non-participating party. That could provide motivation for a gradually increasing scope of international participation.

Nothing about naval nuclear weapons partitioning will be easy. The alternative, however, is to live in a world with two continuing types of unprecedented risk. One risk is that a third party might trigger a nuclear weapons exchange between other countries, either by mistake or in extreme circumstances by design. The other risk is subtler but in the long run perhaps equally dangerous. That is that just the possibility of a third party triggering such an exchange would put it in a position to resist persuasion to join an international trend towards reducing nuclear weapons holdings down to the levels that threaten eventual unacceptable damage rather than launch-on-warning leading to virtual annihilation, or perhaps to eliminate assembled nuclear weapons holdings altogether. Some progress in one of those directions is important in the long run, for the probability per unit time of massive nuclear devastation must be reduced faster than inversely with time in order to avoid an eventual cataclysm.

Clark, Bryan. 2015. The emerging era in undersea warfare,

For more information on partitioning, see downloadable pdf Is a Naval Nuclear Arms Race with China Inevitable?

Dr. Clifford Singer is the director of the Program in Arms Control & Domestic and International Security (ACDIS). Email:
January 31, 2017

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