What "closure" actually means
Closure is not a binary. The relevant scenarios are: (1) sustained harassment producing voluntary self-rerouting by major shippers, (2) selective targeting of Israel-linked or US-linked vessels, (3) full suppression of traffic through the strait, (4) limited mining of approaches. Each has different costs, different reversibility, and different probabilities.
Why full closure is unlikely
- Iran's own oil exports flow through Hormuz; closure imposes symmetrical costs.
- Closure would require sustained suppression of a 39 km strait against the largest naval presence in the region.
- The political cost of being the actor that broke the global energy market exceeds the policy benefit.
- China — the principal buyer of Iranian crude — would not be silent.
Why partial disruption is routine
Partial disruption — vessel boardings, harassment of named vessels, drone shootdowns, mining incidents — is the historical norm during periods of US-Iran tension. The pattern is decades old and has not produced durable closure.
What would actually follow even a partial closure
- Oil prices: an immediate spike with a risk-premium component; the size depends on credibility of restoration.
- Shipping: rerouting where possible, port-of-loading shifts where not.
- Strategic reserves: coordinated SPR/IEA releases to offset price moves.
- Diplomatic: an immediate, accelerated mediation push by every actor with skin in the game — Oman, Qatar, China, EU, Switzerland.
- Military: increased US and allied naval presence; specific escort or sweep operations as required.