In the narrow waters where the Red Sea meets the Gulf of Aden, a regional conflict has reached out to touch the arteries of global trade. Yemen's Houthi movement, backed by Iran, struck two Saudi oil tankers this week and declared a maritime embargo against Saudi Arabia, citing blockades and airstrikes on Sanaa as justification. The Bab el-Mandeb strait — a 32-kilometer passage through which a quarter of Asia-Europe container traffic flows — now sits at the center of a confrontation whose consequences extend far beyond the combatants. What happens in these waters does not stay in these waters.