Iran’s armed forces have blocked 30 vessels from the Strait of Hormuz since August 22, escalating an Islamic Revolutionary Guard Corps Navy campaign that has blacklisted 45 tankers since August 24 for alleged non-compliance with Iranian transit rules. Ships must now coordinate entry with Iranian authorities, pay transit fees and stay in approved corridors after IRGC officials said on August 28 and 29 that no vessel may pass without prior permission, clashing with the US position that the waterway should remain open under maritime law. Daily traffic, previously more than 100 ships and reported earlier near 125, has fallen to single digits, tighter than an earlier wartime estimate of about 25. The crackdown followed the July 8 collapse of a June 2026 US-Iran memorandum meant to ease transit; US Central Command has run dozens of interdictions against Iranian-linked shipping, and some operators have switched off Automatic Identification Systems. The broader conflict, which began after US and Israeli strikes on Iran on February 28, 2026, had already driven VLCC rates as high as $650,000 a day and, on CREA’s reckoning, added as much as $330 billion to seaborne oil, fuel and LNG import costs from March through August 2026, with Brent averaging about $93 a barrel, Iranian exports down about 85% to roughly 250,000 barrels a day, and deep cuts in Middle Eastern refining and Hormuz tanker flows.