At the narrow throat where the Red Sea meets the Gulf of Aden, a militia-backed offensive is testing whether a non-state actor can seize one of the world's most consequential maritime passages. The Houthis, sustained by Iranian support, are pressing toward a port city near the Bab al-Mandab Strait — through which a significant share of global commerce flows each year — in a move that would transform their capacity from disruption to dominion. What began as Yemen's internal war is now reaching outward, threatening to reshape the economics of global trade and the geopolitics of an entire region.