Last October, satellite images captured the distinctive outlines of some powerful new weaponry at a Saudi runway used for military strikes in Yemen. Three Wing Loong drones had appeared, Chinese-made replicas of the U.S. Predator with a similar ability to stay aloft for hours carrying missiles and bombs.

The same month, another Chinese military drone, the CH-4 Rainbow, appeared in a photo of an airstrip in Jordan near the Syrian border. Other commercial satellite images have since revealed Chinese strike and surveillance drones...