Many people have asked me what I think the odds are of an imminent major US-Russia nuclear war. My current estimate is about the same as losing in Russian roulette: one in six. The goal of this post is to explain how I arrived at this estimate. Please forgive its cold and analytic nature despite the emotionally charged topic; I'm trying not to be biased by hopes, fears or wishful thinking.

My estimate is 30% x 80% x 70% ~ 1/6, as illustrated in the figure and explained below. The horizontal axis roughly corresponds to levels of escalation, while the vertical axis corresponds to how favorable outcomes are to the two sides.

Possible outcomes

To estimate the odds of pulling a spade out of a deck of cards, it's important to know how many suits there are. To estimate the odds that the current unstable situation ends up in the "KABOOM" outcome (a major US-Russia nuclear war that might cause nuclear winter and kill most people on Earth), it's similarly important to know what other reasonably stable outcomes it's competing against. The shorthand labels I've given these outcomes (grey boxes) should't be taken too literally: "Kosovo" & "Vietnam" refer to scenarios where one side wins outright (breakaway succeeds & Goliath is expunged, respectively). "Libya", "Korea" & "Finland" refer to intermediate outcomes involving simmering war, frozen war and full peace, respectively. I'm not showing the "Cuba" outcome (invasion averted by negotiated agreement) that was on the table in December 2021, since it's now off the table, as are resumed EU-Russia gas exports via the Nordstream pipelines.

Escalation dynamics

The grey ellipses represent relatively short-lived situations. We are currently in a vicious circle in the form of a self-perpetuating escalation spiral: since "Kosovo" is deemed unacceptable by Ukraine and the West while "Vietnam" is deemed unacceptable by Russia, both sides double down and escalate further whenever they fear losing. Such escalation has been both quantitative (more weapons, more mobilization) and qualitative (e.g., novel sanctions, heavier weapons, longer-range weapons, attacks inside Russia, scaled-up attacks on civilian infrastructure, shelling of a nuclear power plant, assassinations, sabotage of gas pipelines and Europe's longest bridge, annexations, and escalatory rhetoric about nuclear use). My assessment is that Russia, whose...

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