The Houthis have grown from a small northern Yemeni militia into one of the biggest armed forces in the Middle East, which is bad news for global shipping, Saudi Arabia, and Israel.

• Houthi fighter numbers have jumped from 30,000 a decade ago to 350,000 today — bigger than Saudi Arabia's or Israel's forces, and second only to Iran and Egypt in the region.
• Years of war against Yemen's own government toughened them instead of wiping them out, teaching them guerrilla and mountain fighting and how to use captured weapons.
• Money followed: from a few million dollars in the late 1990s to a billion-plus a year from taxes, seized businesses, and oil, plus Iranian weapons and training.
• They now sit on one side of the Red Sea chokepoint while Iran controls the Strait of Hormuz, putting Saudi Arabia in the middle of both.
• Since late 2023 they have hit 100 commercial ships from more than 60 countries, often with no real link to Israel despite claiming they were acting over Gaza.

Outlook: With Houthi forces pushing further along Yemen's Red Sea coast and renewed fighting with Saudi Arabia, pressure on global shipping is set to rise, and Western governments face a choice between confronting them now or facing a far larger force later.