The proximate cause is growing fear of conflict with Iran. Tensions have climbed steadily since America withdrew last year from the agreement struck in 2015 that imposed limits on Iran’s nuclear programme. In May four oil tankers were sabotaged near the uae port of Fujairah. America blamed Iran. The Emirati foreign minister, in a sign of his country’s nervousness, says it is too early to assign blame. “The uae are playing it very cool because they understand how vulnerable they are,” says a Western defence official.