On October 1, the Capitol Hill weekly Roll Call ran a ridiculous commentary by an anti-nuclear activist arguing that the Navy was seeking a budgetary “bailout” at the expense of its sister services to buy more ballistic-missile submarines than it needs. The boats would replace the current Ohio class of subs, which provide the most survivable part of the nation’s nuclear deterrent. The commentary was full of misleading statements, like the assertion that “the contract to buy the Navy’s subs has raced ahead” when in fact construction of the lead vessel was recently delayed by two years. The fundamental flaw in the piece, though, is that the author clearly doesn’t understand how nuclear deterrence works. I taught that subject at Georgetown University for some years, so I’d like to briefly explain why it dictates a future ballistic-missile submarine force of at least 12 boats.

The main goal of U.S. nuclear strategy is to prevent war. Nuclear weapons are so destructive that if even a handful of attacking warheads managed to penetrate U.S. defenses, it would be the greatest catastrophe in the republic’s history. Millions of people might die in the first hour of war. Because scientists have never devised a reliable way of intercepting all — or even most — of the warheads that might be launched in a major nuclear exchange, policymakers have been forced to rely on a strategy of deterrence. Simply stated, deterrence threatens horrible retaliation in response to nuclear attack. The assumption is that no sane leader would launch a suicidal attack, so America must have a retaliatory force that can ride out a first strike and then respond in a devastating but proportional manner.

Ballistic-missile submarines are central to this strategy because, unlike manned bombers and land-based missiles in silos, enemies can’t find them when they are at sea. Obviously, the biggest goal of any aggressor in a nuclear attack would be to destroy the U.S. retaliatory capability, so if that isn’t feasible then the attack is very unlikely to occur in the first place. That is why the current fleet of Ohio-class subs are optimized for accomplishing just one mission: staying hidden until they are called upon to punish an aggressor. The submarines are extremely stealthy, and their successors will be even more secure to guard against any breakthrough enemies might achieve in undersea detection.

The commentary in Roll Call contends that “the Pentagon needs to resize the sub program with the understanding that the U.S. can meet today’s security challenges with fewer nuclear weapons at less cost.” That statement is misleading on two counts. First, the Navy already has reduced the number of ballistic-missile subs in the fleet from 18 to 14 in response to the end of the Cold War, and it plans to further reduce the force when the Ohio replacement becomes operational to a mere dozen boats. Second, the next-generation subs for which the Navy is rightly seeking extra money will not be designed for dealing with today’s security challenges, but tomorrow’s.

Nobody can say what kind of threats the nation’s nuclear force will need to deter 20 years from now. What we can say with near certainty is that preventing a nuclear exchange will remain the top priority of U.S. strategy. So what the nation needs in the sea-based component of its future deterrent force is a retaliatory capability that no enemy could conceivably destroy in a surprise attack. The author says eight boats would be enough, because they could carry “more than 1,000 warheads.” That is fallacious reasoning. The nation would obtain a much more credible deterrent by dispersing the same number of warheads across a dozen or two dozen subs, because what matters in nuclear strategy isn’t how many warheads you have before an attack, but how many you have after. It’s the warheads that survive the attack that deter it from occurring in the first place.

The Navy arrived at the number of a dozen submarines after extensive analysis based on the character of potential threats in the 2030s and beyond, the operational features of future subs, the requirements of national strategy, and the logistical demands of sustaining the fleet at sea. One very important factor in its thinking was the kind of innovations that might enable enemies to find the subs more easily. It was concluded that a force of 12 subs, perhaps eight or nine of which might be at sea on any given day, was the optimum tradeoff of capability and affordability. Any less would simplify an aggressor’s targeting challenge in a surprise attack — potentially depriving the U.S. of its most potent deterrent or forcing it to retaliate in a disorganized fashion.

Does that make the Ohio replacement program expensive? Yes it does — but nowhere near as expensive as the cost of even one nuclear warhead falling on an American city. Buying the right number of ballistic-missile submarines for future deterrence is much more important than getting the Army another tank or filling out the Air Force’s fighter squadrons. Nuclear deterrence is about national survival. Trying to save money by purchasing a less capable deterrent would be really, really dangerous.