Through 2026 the United States and Iran traded blows in the open — American strikes flying from bases in Jordan, Bahrain, Qatar and the UAE, Iran answering against those same Gulf bases and repeatedly closing the Strait of Hormuz. That war has stayed conventional. This model asks the harder question: what if Washington crossed the nuclear line? Iran holds no warheads to answer in kind, so the escalation runs sideways — into the Gulf states hosting American forces, and toward the powers that stand behind Tehran.
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 — United States launches a first strike on Iran — 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: 7.3 million (typical run: 5.5 million–9.5 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 | United States | Iran |
|---|---|---|
| Nuclear warheads | 5,500 | — |
| Avg. warhead yield | 335 kt | — |
| Delivery legs (triad) | 4 | — |
| Automated "Dead Hand" | No | No |
| Population | 331.0 million | 84.0 million |
A strike is never just between two countries. These are the nations the model most reliably pulls into the United States–Iran war (share of runs in which each is drawn in):