Mutually Understood Deterrence (MUD): How Nations Now Navigate the Threat of Nuclear War
Mutually Assured Destruction (MAD), a term coined by a strategist named Donald Brennan in 1962 while working in Herman Kahn’s conservative-leaning Hudson Institute, continues to define international politics in the atomic age. MAD’s thesis is simply that: any head of state who provokes “nuclear war” against an enemy state that also possesses nuclear weapons, virtually guarantees the destruction of his own nation when the enemy launches a reflexive retaliatory strike. After nearly eight decades of international politics in the age of nuclear weapons, it is clear that MAD still largely holds true as a theory of deterrence, but it is also clear that all nuclear threats—even those against a non-nuclear nation—are serious threats to all nations. A footnote to MAD—call it Mutually Understood Deterrence (MUD)—emphasizes the increased role that “bluffing” (as defined in game theory) plays regarding the threat of nuclear war. MUD, when synthesized with insights from calculus and the Nobel-Prize winning economic and political theories of Daron Acemoglu and James Robinson—developed to explain why nations fail—ultimately generates one more reason to advocate, internationally, for the spread of democratic institutions.
MAD and Game Theory
As of the summer of 2025, the atomic bomb will only be 80 years old. In retrospect, it’s astonishing how quickly atomic bombs were combined with early computing and rocket technology to create Intercontinental Ballistic Missiles (ICBMs) capable of causing devastating thermonuclear solar flares on the surface of the Earth. Between 1945 and 1960 the United States and the Soviet Union designed and tested weapons of increasing lethality until both reached the destructive outer limits of a single explosion.1 By 1962, when Brennan developed the concept of MAD, both the Soviets and Americans moved from development stage to the mass-production stage, after which it became possible for both the U.S. and the USSR to completely destroy each other many times over, a process termed overkill.2 The destructive capacity of Russia’s nuclear arsenal, and therefore Russia’s relationship to MAD, survived the collapse of the Soviet Union in 1991.
In an age of hyperbole, it’s easy to think that the destructive power of thermonuclear weapons might be exaggerated. It is not. MAD is not based around lower-grade “tactical” nuclear weapons; it is derived from studying nation-ending military technologies. Consider these passages, about the destructive power of three modern Russian submarines in a wargame simulation, as described in Annie Jacobsen’s Nuclear War: A Scenario:
Two of the three submarines are K-114 Tula, with the NATO reporting named Delta-IV. These nuclear-powered, ballistic missile submarines have long served as a workhorse of the Russian submarine fleet. The third is a newer Borei-class sub, faster and stealthier than its Soviet-era predecessors. Each submarine carries sixteen nuclear-tipped missiles; each missile carries four 100-kiloton warheads in each warhead bus, meaning there are 192 warheads here inside these three Russian submarines. Three submarines. With a payload of 19.2 megatons of explosive yield (p. 237).
Jacobsen goes on to note that it takes only eighty seconds for each submarine to launch every missile it carries. They really do have the capacity to effectively destroy the entire United States in just a few minutes. “It is the astonishing speed,” Jacobsen writes “with which ballistic missile submarines can launch nuclear weapons, and hit multiple targets nearly simultaneously, that makes them the handmaidens of the apocalypse. Time and again, declassified nuclear war games have demonstrated that if deterrence fails, this is how it ends” (p. 238).3 Here is how Jacobsen describes the effect of a single such bomb were it to be dropped on the Pentagon:
A 1-megaton thermonuclear weapon detonation begins with a flash of light and heat so tremendous it is impossible for the human mind to comprehend. One hundred and eighty million degrees Fahrenheit is four or five times hotter than the temperature that occurs at the center of the Earth’s sun.
In the first fraction of a millisecond after this thermonuclear bomb strikes the Pentagon outside Washington, D.C., there is light. Soft X-ray light with a very short wavelength. The light superheats the surrounding air to millions of degrees, creating a massive fireball that expands at millions of miles per hour. Within a few seconds, this fireball increases to a diameter of a little more than a mile (5,700 feet across), its light and heat so intense that concrete surfaces explode, metal objects melt or evaporate, stone shatters, humans instantaneously convert into combusting carbon.
The five-story, five-sided structure of the Pentagon and everything inside its 6.5 million square feet of office space explodes into superheated dust from the initial flash of light and heat, all the walls shattering with the near-simultaneous arrival of the shock wave, all 27,000 employees perishing instantly.
Not a single thing in the fireball remains. Nothing. Ground zero is zeroed.
No country possesses a defense force against ICBMs, thus the above scenario would apply to every city in the United States.
John von Neumann (1903–1957), the genius who worked on the first atomic bombs at Los Alamos, then helped to develop the thermonuclear weapon (H-bomb), and if that were not enough pioneered the principles behind modern computing, along with Game Theory as a way of avoiding full scale thermonuclear war. In fact, von Neumann’s 1944 book (with Oskar Morgenstern) Theory of Games and Economic Behavior was only written seemingly as a Plan B for avoiding unwinnable conflicts. Von Neumann’s first choice for keeping peace in the nuclear era involved an American first strike—astonishingly, in the aftermath of WWII, von Neumann wanted to eradicate Soviet nuclear capability with a first strike. In his biography of von Neumann, Ananyo Chattacharya wrote:
By 1946, von Neumann was predicting that devastating nuclear war was imminent. “I don’t think this is less than two years and I think it is less than ten,” he wrote … on 4 October that year. His answer was preventive war—a surprise attack that would wipe out the Soviet Union’s nuclear arsenal (and a good number of its people too) before the country was able to retaliate. “If you say why not bomb them tomorrow, I say why not today?” he reportedly said in 1950. “If you say at 5 o’clock, I say why not one o’clock?’”4
That a man of von Neumann’s intelligence advocated for a nuclear first strike against the Soviets before the Soviets could develop nuclear parity should give us pause. Although von Neumann’s timeline was off, he could still easily be correct that America’s failure to use nuclear weapons to prevent the development of nuclear weapons by other “players” could mean that we are all locked in a game where everyone loses if anyone launches their nukes.
Game Theory and Bluffing
In Game Theory, a “game” is defined as a situation wherein two or more “players” look to optimize their own results within the confines of defined rules. One of the most interesting aspects of Game Theory is that, if a game is played enough times and there is some sort of learning mechanism involved (through communication/feedback between the players), then an optimal strategy will eventually be reached by players without any kind of centralized authority moving players toward that strategy. If one player stumbles upon a winning strategy, then every other player will have to either adopt that strategy or fall behind. And if no player has anything to gain by unilaterally changing strategies, the game is said to be in a Nash equilibrium, a concept developed by the mathematician John Forbes Nash, Jr., who was portrayed in the film A Beautiful Mind.5
MAD prevents the evolution of strategy because every outcome leads to complete annihilation.
In game theoretic models of international relations, the other player is another nation state, and if they have nuclear weapons, and so do you, it can lead to an arms race resulting in something like a Nash Equilibrium, such as the one that kept the U.S. and USSR in a Cold War nuclear freeze called the “balance of terror,” or Mutual Assured Destruction—MAD—for nearly three-quarters of a century. Popular films such as Fail Safe and Dr. Strangelove reinforced the counterpoint to deterrence, namely that one slip-up, or false-positive identification leading to a counterstrike could lead to nuclear Armageddon. That hasn’t happened yet. MAD has worked because neither side has anything to gain by initiating a first strike against the other nation—the retaliatory capability of each being such that a first strike would most likely lead to the utter annihilation of both countries (along with much of the rest of the world). Here is how former Secretary of Defense Robert S. McNamara described it:
It’s not mad! Mutual Assured Destruction is the foundation of deterrence. Nuclear weapons have no military utility whatsoever, excepting only to deter one’s opponent from their use. Which means you should never, never, never initiate their use against a nuclear-equipped opponent. If you do, it’s suicide.
The logic of deterrence was first articulated in 1946 by the American military strategist Bernard Brodie in his appropriately titled book The Absolute Weapon: Atomic Power and World Order, in which he noted the break in history that atomic weapons brought with their development: “Thus far the chief purpose of our military establishment has been to win wars. From now on, its chief purpose must be to avert them. It can have almost no other purpose.”
The game evolves in the favor of the player(s) that develop the greatest reputation for psychopathic behavior.
This leads to the central conceit of MAD, which is that thermonuclear war is so destructive that the game can only be played once. MAD prevents the evolution of strategy because every outcome leads to complete annihilation. As the rogue AI, “Joshua” tells viewers after running through WWIII scenarios at the end of the 1983 movie Wargames “The only winning move is not to play.” Or, as von Neumman and Morgenstern wrote about two hypothetical poker players “If their hands are equal, no payment is made.”6
Conventional wisdom holds that MAD prevents game-playing, and thus strategizing, but that’s not true. When two players, or multiple players, can destroy each other completely then the game favors whichever individual can bluff most effectively while trying to achieve smaller gains. In thermonuclear poker, nobody is bluffing about their cards, only about their willingness to play them, and this means that the game evolves in the favor of the player(s) that develop the greatest reputation for psychopathic behavior. (I use that term not as literal clinical psychopathy, but figuratively in the sense of willingness to take wild risks without regard to the desires or well-being of others). Some forms of government lead to more psychopathic behavior on the part of their leaders than do others.
Extractive vs. Inclusive Governments
In 2024 Daron Acemoglu and James Robinson won the Nobel Prize in Economics Sciences for their research summarized in their 2012 book Why Nations Fail: The Origins of Power, Prosperity, and Poverty. It explains why “Inclusive” political institutions (democratic governments) are—both subjectively and objectively—superior to “Extractive” undemocratic governments (oligarchies or dictatorships) in delivering prosperity.7
North and South Korea, which share a common ethnicity, a peninsula, a history, a strong mutual distrust, but little else, are featured prominently in Why Nations Fail as evidence of how Inclusive political institutions like those in South Korea outperform Extractive governments like those in North Korea in every conceivable category of prosperity. One component that went unconsidered by Acemoglu and Robinson, however, is that Extractive governments operate under an advantage, in certain conditions, when it comes to international affairs. Precisely because Extractive governments are not accountable to their own citizens, the leader(s) of such governments can engage in the kinds of increasingly psychopathic behavior that facilitates their “bluffing” about the use of nuclear weapons.
A recent example—on December 3, 2024, South Korea’s president, Yoon Suk Yeol, imposed martial law in his country. Yeol’s political motives for doing so remain unclear, but the public’s reaction was swift and decisive. South Koreans, not an excessively rebellious lot, took to the streets, and the democratically elected National Assembly overturned the martial law decree a mere six hours after Yeol declared it. In short order, Yeol found himself impeached, arrested, and criminally charged—a case study in how Inclusive governments prevent dictatorships from forming. Yet, this recent example also highlights a new reality. South Korea lacks nuclear weapons (counting on the U.S. to employ them if needed in the event it was nuked), but even if they did it’s hard to believe that their government would ever use them in a first strike.
Conversely, since the end of the Second World War, North Korea’s government has systematically starved, tortured, isolated, and brainwashed its people into a state of numbed and terrorized compliance. For this reason, Kim Jong Un’s thermonuclear bluff is more powerful than that of any leader in an Inclusive government. No such internal controls prevent Kim Jong Un from waging thermonuclear war, which is why the U.S. maintains the threat of nuclear retaliation if it ever did so.
Mutually Understood Deterrence (MUD)
As of 2025 only nine countries are known to possess a nuclear arsenal. Of the nine, six would be considered “Inclusive” (the U.S., the UK, Israel, India, Pakistan, and France). I will call these “Inclusive Governments with Nukes” (IGWN). Three of the countries (Russia, China, and North Korea), fit under the category of “Extractive” governments, so let’s call these “Extractive Governments with Nukes” (EGWN). Of the nine, only Pakistan challenges the definitional line, but the Pakistani government’s challenges come more from internal political and religious struggles that a weak government seems unable to control.
MAD still largely holds true as a theory of deterrence, but it is also clear that all nuclear threats … are serious threats to all nations.
Mutually Understood Deterrence (MUD) occurs when a state that possesses nuclear arms uses the threat of MAD to deter other states from intervention, while the belligerent state engages in warfare with conventional militaries. MUD favors EGWN’s. For MUD to be an effective strategy a state must:
- Possess a viable threat to launch nuclear weapons.
- Possess a conventional military.
- Have a leader who is believable when “bluffing” about starting a thermonuclear war if his demands are not met.
Launching a strike on a desired territory without these conditions being met can be disastrous for the people in power. In 1991, Saddam Hussein controlled a viable military, though without being able to make a nuclear threat his invasion of Kuwait was met with a conventional military response from the United States and 34 other countries.
Russia’s historical grievance with Ukraine is the same as Iraq’s with Kuwait. Yet, when Russia invaded Ukraine in 2022 no nations supplied any military forces in to drive the Russians out. The critical difference is clear: Russia possesses a thermonuclear arsenal, and Iraq did not. Further, when Russian President Vladimir Putin threatened nuclear Armageddon if any NATO countries directly intervened, their leaders took his statements very seriously.
What to do? Foreign Policy Calculus
Politicians rarely understand calculus, so they often mistake equilibrium for stasis. In the same way that that the immune system acts as a logarithmic function in the early stages of HIV infection—thus countering the exponential growth of the virus8—diplomacy and military support can clear away tensions between nations. (A logarithmic function is a process or scale that increases by powers of a base number, such as 10, such that on a logarithmic scale the difference between 1 and 10 is the same as between 10 and 100, as each increases by a factor of 10, in contrast to a linear scale, where the difference between 1 and 10 is the same as between 10 and 19—a constant addition of 9, compared to multiplying by 10.)
If Russian ICBM’s ever strike U.S. soil, then Ukraine will not seem worth the fight.
To abandon diplomatic efforts in a time of peace is the same as abandoning the immune system in the early stages of an HIV infection; it dooms the patient to an early death. America’s withdrawal from Afghanistan in the summer of 2021 showed the disastrous effects of removing a logarithmic function in a state threatened by Islamist insurgents. In the age of MUD—as it is with an HIV infection—the logarithmic function must be strengthened earlier on.
Understanding MUD makes the current situation clearer. During their notorious February 28th argument in the White House, U.S. President Donald Trump warned Ukraine’s president Zelensky that “You’re gambling with World War Three.” He’s not wrong. If Russian ICBM’s ever strike U.S. soil, then Ukraine will not seem worth the fight. Yet, giving in to Russia’s demands also turns MUD into a viable strategy for the heads of other EGWNs (China, Iran, North Korea). Since 2022, U.S. money and weapons provide a logarithmic function in Ukraine to Russia’s exponential aggression. Removing that function, in the face of a thermonuclear threat, gives credence to MUD.
As of 2025, it seems unlikely that North Korea meets the three criteria for MUD. North Korea has nuclear weapons and a dictator, but if they wish to annex South Korea rather than just destroy it, they will need a stronger conventional military. China, however, does meet all of the MUD criteria. If Russia can claim Ukraine—or most of it—then China could likely use the threat of thermonuclear war—along with a large conventional military invasion—to take Taiwan.
MUD’s influence can be lessened in two ways:
- By preventing the spread of thermonuclear weapons
- Preventing the development of Extractive governments.
As a complement to MAD, MUD helps to clarify an emerging and disturbing international trend, and adds another crucial reason to support Inclusive governments. When playing the international nuclear game, it’s crucial to make sure that the rules don’t change to the advantage of your adversaries.