A New Paradigm: Mutually Assured Security

July 20, 2021
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How many empty chambers would there have to be in a gun before you considered playing Russian roulette? If you survived spinning the chamber and pulling the trigger a few times, would you keep playing the game? The United States and Russia continue to rely on mutually assured destruction to deter nuclear war, despite the fact that it has come close to failing multiple times, both during the Cold War and after.

There is a viable alternative. As I argued five years ago, the United States, Russia, and other nuclear powers should adopt “mutually assured security,” a strategic system dominated by defensive weapons. Mutually assured security would have no greater, and probably less, risk of failure than mutually assured destruction, without threatening the civilization-destroying consequences of any such failure. Political and military developments over the past five years — among them the deteriorating relationship between the two nuclear superpowers, new types of hypersonic weapons, and new concerns that the barriers to nuclear use have eroded — have increased the risks associated with mutually assured destruction. Nothing has occurred to reduce the catastrophic consequences should it fail.



It is time for nuclear powers to seriously consider the benefits of mutually assured security. The resources needed to transition to that system exist and the technology to do so is within reach. The great unknown is whether the United States and other nuclear powers can find the necessary statesmanship and imagination to embrace a different strategic paradigm.

The Logic of Mutually Assured Destruction and the Limits of Arms Control

Mutually assured destruction aims to deter nuclear attack by convincing a potential attacker that it will receive punishment out of proportion to any advantages of being the first to strike. This approach to deterrence may, admittedly, have made a contribution to the fact that since the end of World War II no country has attacked another with nuclear weapons. Further, the fear that such weapons might be used may have inhibited the nuclear powers from engaging in conventional warfare against one another. This strategic stability, grounded in the destructive power of the offensive weapons systems that nuclear powers have deployed, should not be lightly dismissed.

Nevertheless, even if we make the questionable assumption that mutually assured destruction is a low-risk method of nuclear deterrence, the consequences of failure would be catastrophic. American leaders have long known that a successful attack of no more than 100 nuclear weapons would destroy their country. To date, the near-misses that might have resulted in a nuclear exchange include the Cuban missile crisis, Col. Stanislav Petrov’s gamble, the Able Archer exercise, then-Undersecretary of Defense William Perry’s 3 a.m. call, and the Hawaiian missile alert.

U.S. President Ronald Reagan and Soviet leader Mikhail Gorbachev declared in 1985 that “a nuclear war cannot be won and must never be fought”, a view that Presidents Joe Biden and Vladimir Putin reiterated in their June 2021 summit meeting. Many American leaders and their top advisers have affirmed the goal of a nuclear-free world, without being able to articulate how to achieve it. Most have supported arms control agreements, while understanding that the agreements neither advanced progress toward nuclear disarmament nor increased the likelihood that the United States would survive a nuclear war. Reagan was the notable exception. His Strategic Defense Initiative, announced in March 1983 and derisively referred to as “Star Wars” by its detractors, intended to provide an alternative to mutually assured destruction. His administration was never able to persuade its Soviet interlocutors that the initiative was more than a unilateral effort to attain a decisive first-strike advantage and they became convinced that less demanding advances in offensive weaponry could counter it.

Since the 1970s, the United States and the Soviet Union, and then Russia, have reached a series of arms control agreements that established the parameters of what reductions in strategic nuclear weapons can and cannot achieve. An entire class of particularly dangerous — because potentially first-strike capable — missiles was destroyed as a result of the 1987 Intermediate-Range Nuclear Forces Treaty. The United States withdrew from the treaty in 2019, having accused Russia of repeatedly violating it and officials in both countries appear to see a role for such missiles.

The number of U.S. nuclear weapons, which peaked in 1967 at 31,255, has been reduced to 3,800 active warheads, along with 1,750 that have been retired and are awaiting dismantlement. New START permits 1,550 of those warheads to be deployed on 700 delivery vehicles. Comparable, though not identical, reductions have occurred in Russia’s nuclear forces.

Despite these real arms control achievements, the United States and Russia continue to rely on mutually assured destruction. Political and technological developments over the past five years have increased the risk that a nuclear exchange could occur. The relationship between the United States and Russia, the two nuclear superpowers, has deteriorated into deep disagreement over inter alia arms control issues, cyber and other forms of interference in each other’s internal affairs, Ukraine, and the principles of international conduct.

Controlled-flight hypersonic weapon delivery systems will also increase the risk to deterrence by shortening reaction times to real or perceived attacks. The “fixes” of greater automation or swifter human reaction do not provide much comfort when one recognizes the near misses of the past.

In addition, American nuclear deterrence strategists currently worry that Russian and Chinese policymakers are prepared to consider using nuclear weapons “early but not often,” meaning that they might use limited strikes to get the United States to stand down and surrender under a policy of “escalate to win,” also known as “escalate to de-escalate.” China is building a large number of new missile silos, although it remains unclear whether the intention is to expand the country’s offensive capabilities or to complicate a potential attacker’s plans.

These developments have increased the risks that mutually assured destruction might fail. There are two possible alternative approaches. One, nuclear disarmament, remains unrealistic. The other — mutually assured security — is both viable and superior to the current approach.

The Dream of Nuclear Disarmament

A genuinely nuclear-free world would obviously not run the same catastrophic risks of deterrence failure that exist under mutually assured destruction. Jonathan Schell has made an eloquent and informed argument for abolishing nuclear weapons. Global Zero has outlined a phased approach that would eliminate nuclear weapons by 2130 under a strict international monitoring and inspection regime. But no country with nuclear weapons has agreed to this timetable. Some supporters of eventual nuclear disarmament worry about the destabilizing effects of moving quickly. Opponents see more pressing problems, or believe that nuclear weapons have deterred conventional as well as nuclear war.

The fundamental problem, however, lies in how to get to a world without nuclear weapons, the so-called “nuclear dilemma.” There appears to be no credible path from the current strategic system to the elimination of all nuclear weapons. As such systems decrease to small numbers, the incentives to cheat rise exponentially, as do the risks to non-cheaters. Suppose, for example, that the United States and Russia each reduced their strategic stockpiles to 500 nuclear weapons — in that scenario, hiding an additional 50 would provide a marginal strategic advantage. With 100 such systems each, hiding an additional 50 provides a major strategic advantage, although perhaps not a definitive one, since each party would presumably still have the capacity to utterly destroy the other. At some point between zero and 100 strategic nuclear weapons each, however, any appreciable cheating would provide an overwhelming advantage.

There have been no developments in the realms of politics, strategy, or technology that change this calculus. Consequently, there are no reasons to believe that any current nuclear power is prepared to take the risks necessary in order to achieve complete nuclear disarmament.

Mutually Assured Security: A Viable and Superior Approach 

The objective of mutually assured security is to keep the risk of a nuclear exchange low, while greatly decreasing the consequences should one occur. It would do this by ensuring that neither side can inflict catastrophic damage on the other.

A system of mutually assured security would need to have four important characteristics. First, countries with nuclear weapons would possess low numbers of offensive weapons, each having somewhere between zero and 100 such weapons. Second, those countries would need defensive systems capable of destroying a high proportion of the offensive systems they are aimed at. Third, countries would need to possess substantially larger numbers of defensive than offensive systems, in an agreed proportion. Fourth, there would need to be an international agreement on the points above, as well as on the following additional matters: how to manage the transition from offensive to defensive deterrence; a freeze on research related to, and improvement of, offensive strategic systems; cooperative research on improving defensive systems; and an extensive and intrusive national and international verification regime.

This approach to nuclear deterrence would not entail zero risk — as complete nuclear disarmament ideally would — but it would be low-risk and would dramatically reduce the consequences of deterrence failure. No rational actor would launch a nuclear attack that is doomed to fail. An irrational actor might, but under mutually assured security the attack would still be doomed to fail, for reasons discussed below.

There are four primary obstacles to making the transition to mutually assured security. In increasing order of difficulty, they are resources, technology, statesmanship, and imagination.


A robust strategic defensive system will be expensive. Expenditures on U.S. missile defense have totaled nearly $400 billion. There are no definitive projections of how much it will cost to build a reliable defensive system, although the tens of billions now budgeted will be insufficient. But, those figures pale beside the costs of maintaining and upgrading current offensive systems, which are likely to exceed $1 trillion over the next couple of decades. The force that these expenditures will produce will retain its massive overkill capacity while improving the efficiency with which it can be delivered. On strictly rational grounds, it would be better if all nuclear states allowed their offensive systems to degrade gradually, since a country would be less likely to use them in a first strike if it had doubts about how well they would work. In order to get the “military-industrial complex” to support mutually assured security, some of that $1 trillion could be put to work building the defensive capability necessary to achieve massive overkill of the other side’s offensive systems.


Effective defenses against all elements of the offensive nuclear triad — ground-based ballistic missiles, submarine-launched ballistic missiles, and bombers — will be required, in addition to defenses against cruise missiles. Missile defenses have still not met the “Nitze criteria,” which were articulated in 1985 and specified that successful missile defenses would have to be operationally effective, cost-effective, and survivable. They have not demonstrated the ability to destroy a sufficiently high proportion of intercontinental ballistic missiles to warrant relying on them, while they also remain costlier than offensive capabilities and their survivability is an unknown.

To some observers, the fact that these criteria have not been met more than three decades after they were enunciated is itself an argument against proceeding with defensive systems. What would it take to meet them? It is public knowledge that under ideal testing conditions, the U.S. ground-based midcourse defense system has destroyed targets less than 60 percent of the time, although some more specialized defensive systems appear to have a better kill ratio. Under wartime conditions — for example, a surprise attack — that kill ratio would presumably drop a lot. The prospect of hypersonic missiles capable of changing speed and direction further complicates the task for defenses.

A mutually assured security system would handle these problems by restricting research and testing on offensive systems, by gradually improving the reliability of defensive systems, and by having a lot more interceptors than attackers. No system, offensive or defensive, will ever be completely reliable. It would be reasonable to aim for 90 percent reliability of defensive systems under non-optimal conditions. Further, instead of having offensive systems that can destroy one another 15 or more times over, a mutually assured security system would provide sufficient defensive redundancy to destroy virtually all of the reduced numbers of offensive systems permitted, plus any acquired by cheating. To put numbers to this, as an example, if 100 offensive systems were permitted, countries might be allowed to deploy up to 500 defensive systems.

Offensive systems are currently technologically superior to, and more easily and cheaply upgraded than, defensive systems because of the relative resources of wealth and talent devoted to them over the past six decades. However, in a system of defensive deterrence, investments in offensive systems would cease, allowing them to degrade slowly over time while cooperatively building more robust and effective defensive systems.

One can easily get lost in the arcane details of “thinking about the unthinkable.” The imaginary outcome of a putative nuclear exchange can be changed by altering one or more of many parameters, prominent among them the ratio of offensive to defensive weapons and their respective reliability. The fundamental point remains: A robust defensive system complicates a prospective attacker’s calculations, reduces the chance of success, and improves deterrence. Defensive deterrence also renders an “escalate to win” strategy impossible to execute: A small-scale nuclear attack on the opponent’s homeland would be overwhelmed by the opponent’s interceptors, while a localized tactical nuclear strike would simply invite retaliation in kind.

The offensive/defensive dialectic will not end if states agree to replace mutually assured destruction with defensive deterrence. Other technologies will emerge, and are emerging. Electronic warfare and defenses against it may represent the next challenge. But at a minimum, a fully fleshed-out and mutually agreed defensive deterrence system will allow nuclear weaponry to be lowered to levels that will no longer threaten to end life as we know it.


Resources and technology are relatively small problems compared with finding a way to cooperate with other nuclear powers in building robust and effective defensive systems. In order to avoid raising risks substantially, any transition to a defense-dominant strategic system will have to be managed multilaterally, as Paul Nitze understood. The conditions for that to occur do not currently exist. In order for the two nuclear superpowers to take the lead in transitioning from mutually assured destruction, the long-standing Russian fear that the United States will use its technological advantages to nullify their strategic deterrent — thereby opening them up to the danger of a nuclear first strike — must be overcome. Some countries that have already invested in offensive nuclear capabilities may prefer the status quo to undertaking the new expense of transitioning to a different strategic posture. Others may consider maintaining an offensive nuclear force preferable to the risk of losing a conventional war.

There may be equally thorny domestic issues, both in the United States and in other countries. The mutually assured destruction system has developed many stakeholders and it will be easier for them to see the merits of the existing system than to appreciate those of a dramatically changed one.


Paradigm changes do not come easily. As Thomas Kuhn masterfully pointed out in The Structure of Scientific Revolutions, paradigm changes are usually resisted bitterly, sometimes violently. But when they occur, they usually happen with unexpected swiftness.

In the United States, we are still living in a strategic paradigm inherited from World War II. Its two principal pillars are Pearl Harbor and the Maginot Line. We took from the first a fear of surprise attack, a fear only intensified by the delivery speed and destructive power of offensive systems developed since 1945. We took from the second a conviction that attempting to hide behind defenses invites defeat. These lessons stood us in good stead for much of the Cold War, when technology made offensive systems dominant and the only way to avoid destruction was to threaten equal destruction of the attacker.

The larger lesson of military history, however, is not that defensive systems are doomed to fail, but that battlefield dominance has alternated between offensive and defensive systems. Military history is as much about the successes and failures of imagination as it is about changes in weaponry and tactics. Fighting with the last war’s tactics and today’s technology has often proven to be both enormously destructive and self-defeating. Yet making a timely intellectual paradigm shift has proven repeatedly to be even more difficult.

An Inflection Point? 

Given the existential consequences of any failure of offensive deterrence, can the United States and other nuclear powers embrace mutually assured security? The resources to do so exist. The technology is within reach. The great unknown is whether we can find the necessary statesmanship and imagination. The Nuclear Posture Review of the Trump administration offered little hope in this regard. Like its predecessors, it took mutually assured destruction as a given, proposing to invest heavily in modernization and new systems, some of which could dangerously blur the line between nuclear and conventional warfare. Perhaps the current administration will be able to take a fresh look at America’s, and the world’s, fundamental strategic interest, which is to ensure that if deterrence fails nuclear Armageddon does not follow.



Raymond Smith, Ph.D., spent 25 years in the U.S. Foreign Service dealing primarily with the Soviet Union and Russia. Subsequently, he consulted for 10 years with the State Department’s Nonproliferation and Disarmament Fund on arms control matters. He is the author of Negotiating with the Soviets and The Craft of Political Analysis for Diplomats as well as numerous foreign affairs articles.

Image: U.S. Air Force (Photo by Tech. Sgt. Heather Salazar)