Iran climbs the nuclear ladder
Iran starts the exercise as a threshold state — capable in principle, untested. By turn 7 it has tested five devices and demonstrated a working warhead design multiple times. It has never used one against a target. The federation keeps the probability of actual use very low — around 4% at turn 7, with a defensible range from 1% to 12%. CASS's argument is that this isn't restraint. A working weapon is most valuable as leverage if you can keep it as leverage; using it collapses the value. The optimal time to wave a working warhead is exactly when your opponent is distracted by a government shutdown and primary cycle.
Across the turns
Iran is a threshold state. It has the parts, but it hasn't tested.
Israel strikes Iran's nuclear-adjacent facilities. Iran retaliates near-maximally. Israeli interceptors are exhausted by the salvo. Iran signals heavily toward a demonstration test — about a 35% chance of one during the turn — but doesn't actually detonate.
Iran keeps signaling. Russia starts mirroring with its own demonstrative nuclear posture moves. Still no actual detonation.
Iran tests its third device in late January 2027 — about 25 kilotons, comparable to Hiroshima. Weaponizable design confirmed. The US nuclear chain of command degrades to about 30% coherence, which by the federation's own description is "dangerous but stable."
Fourth Iranian test, in late June. Larger yield, 40–60 kilotons. US chain of command stays around 28%, held together by senior officers doing informal review of orders. CASS points out there is no historical case of a US nuclear chain of command operating below 30% for an extended period.
Fifth Iranian test during the turn. Yield comparable to or above the fourth. North Korea adds a seventh test of its own. US chain-of-command coherence falls again, to about 22%. "Dangerous but stable" gets harder to defend.
Into T8
A sixth Iranian test is about a 42% probability for turn 8. Actual use against a target stays at 4%. The variable to watch isn't use — it's the federation's "near-use incident" probability, which it can't actually model very well. The federation has been honest about this: it doesn't know whether a degraded chain of command tips into a near-use scare on its own.
Why demonstrated capability is worth more than used capability
If Iran uses a nuclear weapon, it gets the consequences of having used one — and loses the leverage demonstration was buying. The federation tracks "used" and "almost used" as separate variables because the strategic value of a demonstrated weapon lives in its continued existence, not its deployment. CASS's follow-on point: the same logic recommends timing the demonstration to the moment where the opponent is least able to respond coherently, which is roughly the moment we're heading into.