Methodological exercise by the St. Gallen Endowment's technology team. Not an institutional assessment. Each probability answers: how likely is this scenario to be the dominant crisis trajectory four weeks from the assessment date? They express relative confidence, not precise forecasts. Treat them as a ranking with approximate magnitudes.

Scenario Definitions

Eight mutually exclusive scenarios used by the monitoring system. Scenarios are mutually exclusive at any given assessment point but can transition into one another over time. Probabilities shown are from the latest assessment.

A

Negotiated Exit

7%

4-week outlook

A diplomatic settlement halts military operations before either side achieves decisive military objectives. Requires a credible Iranian interlocutor, willingness to negotiate on both sides, a mediator (Oman, Turkey, or China), and a face-saving formula for both leaderships. Historical analogues: the Kosovo air campaign ending through Russian-mediated diplomacy.

V

Declared Victory

17% (+1)

4-week outlook

Trump declares that US military objectives have been achieved and withdraws American forces. He frames whatever destruction has been inflicted as a decisive victory. Israel continues operating alone but with sharply reduced capability. The war does not end; it transforms into a different war. This scenario requires no Iranian cooperation, no mediator, no mutual agreement — just a single decision by a single person based on domestic political calculus.

B1

Coercive Submission

1%

4-week outlook

Iran capitulates under military pressure within the first two weeks. The regime accepts US/Israeli terms: permanent end to enrichment, ballistic missile limits, and cessation of proxy support. This requires both a collapse of Iranian military capability and a political decision to surrender, which historically almost never happens to regimes that retain any capacity to fight.

B2

Grinding Degradation

5% (+1)

4-week outlook

A sustained US/Israeli air campaign systematically degrades Iran's military infrastructure over 3 to 5 weeks, reducing Iranian retaliatory capacity. Success requires Iranian fire rate to decline measurably week over week and no major escalation beyond what air power can address.

B3

Attrition Stalemate

13% (+3)

4-week outlook

Neither side achieves decisive results. Iran sustains retaliatory fires at a reduced but persistent rate. The Strait of Hormuz remains contested. Oil prices stay elevated. The conflict becomes a war of economic and military attrition, ending when domestic political costs force one or both sides to seek an exit. Historical analogues: the Iran-Iraq Tanker War (1984–1988).

B4

Regional War

24% (-4)

4-week outlook

The conflict expands to include active military engagement by actors beyond the initial belligerents. Qualifying events include Houthi activation in the Red Sea, Gulf state transition to offensive operations against Iran, Hezbollah opening a sustained second front, or third-party military intervention.

C

Regime Fracture

11% (+1)

4-week outlook

Internal divisions within the Iranian state, exacerbated by leadership decapitation, lead to institutional fragmentation. The IRGC, civilian government, and clerical establishment pursue contradictory strategies.

D

Nuclear Sprint

13% (-1)

4-week outlook

Iran, under existential threat, attempts to rapidly assemble and potentially demonstrate a nuclear device using pre-positioned fissile material that survived both campaigns. Lowest probability, highest consequence. This scenario models Iranian nuclear decision-making under existential pressure, not a US nuclear strike. The risk pathway runs through desperation, pre-delegation, and miscommunication, not through deliberate US escalation.

Scenario probabilities for nuclear outcomes are inherently unreliable and should not be used for operational planning. This analysis identifies structural risk factors, not predictive estimates.