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?
Nuclear weapons are used, but the exchange stays regional or tactical rather than becoming a full strategic war. The taboo is broken and thousands to millions die — the world steps to the brink and pulls back.
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: 1.9 million (typical run: 1.4 million–2.4 million).
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):