India, Sept. 1 -- Yemen's historic coffee hub of Mocha once controlled the world's beans, sending "Arabica" across Ottoman and European markets and lending its name to the moka pot. As colonial powers smuggled seeds to Java, India and Brazil, Mocha's monopoly collapsed. Yemen's shift from coffee to water-hungry qat deepened ecological crisis, helping create the conditions that later fuelled Houthi militancy along the Red Sea.

The Red Sea often makes headlines as the launch site for attacks on oil tankers and infrastructure by the Houthi rebels, a political and religious group that controls much of the northern and western areas of Yemen. But the history of this vital shipping route was once defined by the passage of another dark, liquid ...