Houthi territorial advances in September 2026, including seizures of the port of Mocha, Perim Island, and Hanish Islands along Yemen’s Red Sea coast, have strengthened the group’s ability to monitor and target shipping lanes through the Bab el-Mandeb Strait. These gains followed renewed missile and drone strikes on vessels, contributing to sharp drops in daily transits—from typical levels near 30 to lows in the mid-teens or below—while Houthis maintain a declared maritime embargo focused on Saudi-linked traffic and assert that broader navigation remains safe. Trader consensus on Polymarket reflects this pressure through implied probabilities of 11–22% for effective closure (defined by IMF PortWatch data showing a 7-day moving average of 10 or fewer ship arrivals) by late 2026 dates, down from higher readings after initial advances but still elevated by ongoing clashes, Saudi counterstrikes, and regional tensions involving Iran. Potential shifts hinge on further military escalations, naval escort deployments, or de-escalation in Yemen fighting within the resolution windows.