It’s been 75 years since Hiroshima and Nagasaki were incinerated, and 50 years since the Nuclear Non-Proliferation Treaty took effect. And yet the world today is in greater danger of nuclear war than at any time since the Cuban Missile Crisis.

In its confrontation with the United States, Iran appears hell bent on getting nukes, and could do so within a year. If it does, Saudi Arabia and Turkey will almost certainly follow suit. Israel is already armed. Asia has several nuclear hot spots. And in the most frightening scenario, at any point bombs could fall into the hands of terrorists or other “nonstate” groups that are hard to retaliate against and thus deter.

To slow this proliferation of nukes, the world still relies mostly on the Nuclear Non-Proliferation Treaty, known as the NPT, which currently has 191 signatories. Every five years, diplomats gather for a review conference (RevCon), and the next one, in New York, starts in April. Expectations are low, fears are high. If diplomats and the public read up on game theory, their dread would grow more.

When the treaty was negotiated in the 1960s, it was meant to be a grand bargain. The five countries that already had nukes (the U.S., the Soviet Union, the United Kingdom, France and China) would keep them but promise to work toward eliminating them. All other signatories would forswear nuclear weapons in return for help from the big five in using civilian nuclear technology as an energy source. (Israel, Pakistan, India and South Sudan never signed, and North Korea withdrew.)

Has the treaty been a success? Its fans claim that without it even more states might have nukes today. Skeptics worry that the system requires a benevolent hegemon, i.e., the U.S., to police it, but that under U.S. President Donald Trump this credible and predictable benevolence is gone.

If allies — for instance Japan, South Korea or Taiwan — can no longer be absolutely sure that the U.S. would retaliate on their behalf against a nuclear strike on them — say, by North Korea or China — what’s to keep them from wanting to go nuclear themselves? And what’s to keep other adversaries from doing the same as a hedge against such an outcome?

That’s where game theory comes in. It’s a branch of mathematics that’s been used since the 1960s in nuclear scenarios. The initial games included simple classics such as “chicken” and “the prisoner’s dilemma.” One disturbing insight is that, depending on the game, even rational players acting rationally can end up in situations (called Nash equilibria) that are disastrous for everybody.

When analyzed with game theory, the NPT looks like a terrible idea. The problem is it still lets countries of all stripes gain entry-level nuclear technology for civilian use. However, once a country, like Iran, learns to build a nuclear reactor — by enriching uranium — it’s just one small step from making bombs. That in turn forces adversaries to sprint to the same point. The result is a “soft arms race” like the current one in the Middle East.

Game theory also offers plenty of reasons to worry once soft arms races turn into hard ones. That’s because the world has become more complex since the Cold War.

Back then, the U.S. and the Soviet Union used game theory to find a stable strategy for avoiding the worst: mutually assured destruction. (The acronym — MAD — says it all.) It rested on various assumptions. Both sides, for example, must be able to retaliate even after being struck, which is why the U.S., Russia and now also China are so keen to be able to deploy from land, sea, air or even space. By today’s standards, those old games are laughably simple. They had two players, both assumed to be “rational,” an assumption few people make confidently about some world leaders today.

Worse, the number of players keeps growing. So do the permutations of new weapons, such as small nukes for tactical uses or hyper-sonic missiles that give adversaries no time to weigh responses. This leads to a spectacular increase in the possible decisions and responses — and miscalculations.

The math quickly gets complex beyond normal human capacities.Games include, for example, perfectly rational but slippery strategies such as brinkmanship, when actors deliberately “let the situation get somewhat out of hand” just to make it “intolerable to the other party.” The problem is that such situations — such as the skirmishes last year between India and Pakistan, both nuclear powers — can easily go from somewhat, to totally, out of hand.

Another difficult strategy is posturing, to deceive adversaries about one’s own risk appetite (as when Trump tweets about “fire and fury”). Some games also include, quite realistically, a chaotic actor such as nature, more commonly known as “s—- happens.”

One mathematical problem is that many of these games need to be played for an unimaginable number of rounds before a Nash equilibrium becomes clear. That might seem acceptable when game theory is applied to economic problems such as how to design the best type of auction for 5G wireless spectrum. In a nuclear context, it would be game over for Homo sapiens.

But game theory also offers a glimmer of hope. A huge problem, in games and reality, is that players either don’t know, or can easily misread, the minds of their adversaries. This can be fixed by adding a mediator, in effect a trusted adviser who selectively provides and withholds information to the enemies, while introducing strategies such as “regret minimization.”

Let the search be on for such mediators, ideally in time for the RevCon in April. The U.S., Russia and China could also use mediation. The former two casually shrugged off one arms control treaty last year and seem blase about rescuing the only remaining one, called New START, which expires in a year. China, thinking more about power and destiny than survival, is boosting its arsenal to catch up with them.

Everyone involved needs to understand that nuclear war is not a game.

Andreas Kluth is a member of Bloomberg’s editorial board. He was previously editor in chief of Handelsblatt Global.

KEYWORDS nuclear weapons