Yemen's Houthi rebels seized full control of the historic Red Sea port city of Mocha on Thursday, government forces confirmed, as the Iran-aligned militia pushed to lock down one of the world's most critical oil shipping lanes: the Bab al-Mandeb Strait.

A Yemeni military source said Houthi fighters entered Mocha as internationally recognized government troops carried out what officials called a "tactical withdrawal" to regroup. The rebels also seized Zuqar Island and reportedly landed fighters on Perim Island, both inside the strait, and were advancing south toward the town of Dhubab, according to Al Jazeera.

A quarter of the world's oil at stake

Bab al-Mandeb, Arabic for "Gate of Tears," is barely 29 kilometers wide at its narrowest point and separates Yemen from Djibouti and Eritrea on the Horn of Africa. It funnels roughly a quarter of the world's daily petroleum shipments and close to a third of global maritime trade between Asia and Europe via the Suez Canal, according to Euronews. Oil markets reacted quickly, with crude prices jumping on fears that a second global chokepoint could fall under militia control, per The National.

Fighting over Yemen's western coast has killed hundreds in the past week alone, and a Saudi-led coalition backing the government has flown dozens of airstrikes in response. Rashad al-Alimi, head of Yemen's Presidential Leadership Council, called on allies to act, saying "the protection of Yemen's coasts and the restoration of state control over its territory, ports and waters is a joint Yemeni, Egyptian, Arab and international interest."

"They want to transform the area into a situation resembling that of the Strait of Hormuz," said Major-General Sadeq Duwaid, spokesman for Yemen's National Resistance Forces, of the Houthis' ambitions for Bab al-Mandeb.

The seizure lands squarely atop an already-boiling regional crisis: Iran has spent the past week threatening tankers and a "restricted zone" across the Persian Gulf after the U.S. sank five of its oil vessels near the Strait of Hormuz. Analysts warn a simultaneous squeeze on Bab al-Mandeb would leave global shippers with almost no safe route between the Gulf and the Mediterranean.

The United Nations' special envoy for Yemen, Hans Grundberg, warned the country now faces its "gravest risk of full-scale war" since a fragile 2022 truce collapsed the last major escalation, and called on the Houthis to halt attacks on shipping and across borders. Washington accused the Houthis of acting as Iranian proxies to widen the conflict.

Government forces say they are regrouping to attempt to retake the coastline, but with the Houthis now holding Mocha and islands inside the strait itself, Western navies and Gulf states are bracing for the group to attempt the kind of harassment campaign against merchant shipping it waged in the Red Sea in 2023 and 2024 — this time from a position of far greater geographic control.