As the Soviet nuclear arsenal grew, academic theorists justified the triad with the logic of survivability—multiple means of delivering nuclear strikes would make it harder for the Soviets to disarm us with a first strike or to blackmail us with that threat. But, as the Cold War wore on, hardened missile bunkers, surveillance technologies and raw numbers of delivery vehicles increasingly guaranteed the U.S. arsenal’s survival from a Soviet strike. And it became harder to imagine that Communist leaders were crazy enough to bet their state on the proposition that they could find and destroy every deployed U.S. nuclear weapon.

These factors explain the steady decline in the arsenal’s size even before the Cold War’s end. Since then, the case for the triad weakened further. One reason is nuclear weapons’ reduced contribution to peace among great powers. Mutually assured destruction contributes less to peace than other pacifiers—capitalism and trade’s reduction of war’s benefits, nationalism and conventional weapons’ heightening of its costs, and people’s gradual appreciation of these changes.

Second, predictions about waves of nuclear proliferation proved false. New nuclear powers deploy only handfuls of delivery vehicles, most incapable of reaching American shores. China remains uninterested in developing an arsenal that threatens ours, building only enough long-range missiles to achieve minimum deterrence. Russia has proven eager to shift resources from nuclear to conventional forces. Our triad strengthens the hand of Russians opposed to that shift.

Third, in recent decades, the U.S. military has vastly increased its ability to precisely target enemy forces with conventional and nuclear weapons. This dramatically reduces the number and explosive force of the weapons needed to hold enemy targets at risk.

These changes allow a far smaller nuclear force—something like General Cartwright’s proposal for roughly 500 warheads primarily based on submarines—to provide all the nuclear deterrence we need. Unfortunately, strategic arguments cannot themselves end the triad. It survives thanks to bureaucratic inertia and the political pull of its beneficiaries—those in the ranks, the shipyards, production lines, bases, and weapons labs. These forces thwarted the only real attempt to shift to a dyad or monad, which was undertaken in President Clinton’s Pentagon.

Political support for the triad may now be weakening. Nuclear weapons provide the Air Force and Navy with little prestige or budgetary advantage because of their irrelevance to modern war. With their budgets under pressure, service chiefs may see nuclear weapons like step-children taking food from hungry, true sons. Obama’s historically modest defense cuts have already produced Pentagon proposals to shift nuclear weapons funding to conventional programs closer to the service’s core missions. The Air Force wants to develop its new bomber initially without the ability to carry nuclear bombs—a subtle invitation to remove a leg of the triad. The Navy hopes to eventually operate ten ballistic missile submarines rather than the current fourteen. And with each boat’s procurement cost alone now expected to exceed $5 billion, the Navy may have to drastically change its design to protect the rest of its shipbuilding budget.

The Obama administration suggests that it will consider big changes in the nuclear arsenal only as part of a new arms control agreement with Russia. That’s a mistake. The Russians are likely to reduce their arsenal if we cut ours, treaty or not. And we should not give them a veto over our fiscal needs.
The opportunity to reform the triad may not last. A deficit deal might soon limit pressure on the defense budget and thus the military’s willingness to shed nuclear missions. Bigger defense cuts today may induce the Pentagon to kill the triad itself.

Friedman is a research fellow in defense and homeland security studies at the Cato Institute.