Voluntary avoidance of Hormuz by tanker operators achieves, in functional terms, some of the same supply-disruption effects as an Iranian blockade — without requiring Iran to take the naval action that would have constituted a direct casus belli for further US military response.
Approximately 20 million barrels per day transited Hormuz in 2025 — around 20% of global oil supply and 30% of global liquefied natural gas. Voluntary tanker avoidance does not halt all transit, but it reduces throughput and drives insurance premiums on vessels that do proceed to prohibitive levels. Lloyd's of London and other marine war-risk insurers will reclassify The Gulf as a war-risk zone within hours of the strikes, adding several hundred percentage points to insurance costs and making many voyages commercially unviable even if the physical route remains open.
The difference between voluntary avoidance and a formal Iranian blockade is reversibility. Commercial tanker operators are risk-averse but economically rational: if the military situation stabilises or a credible de-escalation signal emerges, traffic will resume within days. A formal Iranian blockade would require negotiated lifting and military verification, potentially taking weeks or months. Voluntary avoidance is therefore a more moderate and more reversible disruption than the worst-case scenario — which is precisely why markets are pricing $80–100 rather than $150–200.
