Punjab, Sept. 10 -- Brent crude closed above $100 a barrel on Wednesday, its first close at that level since May, as the war between the United States and Iran entered its seventh month. Houthi forces have seized a Red Sea port city near the Bab al-Mandab strait.

Two chokepoints, one shipping route

The Bab al-Mandab is the southern gate of the Red Sea, the approach to the Suez Canal. The Strait of Hormuz is the other end of the same trade. A single actor gaining ground at Bab al-Mandab while the Gulf remains contested puts pressure on both ends of the route that carries a large share of the world's seaborne energy.

Shipping does not need to stop for this to be expensive. War risk insurance, longer routing around the Cape, and slower turn...