Ukraine surrendered the world’s third-largest nuclear arsenal in 1994 in exchange for security assurances. That makes a Russian nuclear strike on Ukraine a one-sided event on paper — but Ukraine does not fight alone. The model tests the question that has hung over the war since 2022: does a tactical strike stay contained, or does it finally pull NATO across the line?
Great powers trade strategic strikes. Millions die in the opening hours and radioactive fallout crosses continents. Humanity survives, but the prewar world does not.
Each run starts the same way — Russia launches a first strike on Ukraine — and then the escalation engine plays the alliance cascade forward, decision by decision. Because retaliation, alliance loyalty and doctrine are probabilistic, the 500 runs don’t all end the same way:
Estimated human cost: 2.4 million+ in direct strikes, with billions more at risk from the ensuing nuclear winter.
Modeling note: these pages show the engine’s projected escalation, assuming launched weapons reach their targets. The live 3D simulation additionally rolls probabilistic missile-defense interception, so an individual run there may be less severe. Casualty figures are first-order estimates from capital-population and arsenal data — a floor, not a ceiling.
What each side brings to the exchange, from the simulator’s arsenal data (SIPRI/FAS-derived estimates):
| Metric | Russia | Ukraine |
|---|---|---|
| Nuclear warheads | 6,200 | — |
| Avg. warhead yield | 500 kt | — |
| Delivery legs (triad) | 4 | — |
| Automated "Dead Hand" | Yes | No |
| Population | 144.0 million | 44.0 million |
A strike is never just between two countries. These are the nations the model most reliably pulls into the Russia–Ukraine war (share of runs in which each is drawn in):