New Delhi, July 28 -- collective, public condemnation. Tribes that had long hedged between factions, cutting private arrangements with Houthi commanders to protect their villages, moved together. His case became a line.

That shift is now one of the central dynamics as Yemen edges toward what some analysts describe as a fundamentally different kind of war. On Wednesday, Houthi forces claimed missile and drone attacks on two Saudi oil tankers, extending a maritime campaign that has already pushed Brent crude above $100 a barrel and drawn an explicit warning from Donald Trump that any further strike would be answered by US military action against Iran. But the more consequential change, several analysts said, may be happening on land.

In a...