Three U.S. service members were killed and at least 34 injured in a drone strike in Jordan on Sunday. It’s the latest in a series of attacks in the Middle East by armed militia groups linked to Iran. WSJ’s Sune Engel Rasmussen explains how Iran uses these groups to fight proxy wars and to extend its influence in the region.  Further Reading: - Three U.S. Troops Killed in Drone Attack in Jordan  - U.S. Failed to Stop Attack in Jordan After Mixup Over Drone Identity  Further Listening: - ‘We Were Attacked’: Militants Upend Global Shipping  - Will Israel Face a Second Front?  - Cheap Drones Are Transforming the Battlefield  Learn more about your ad choices. Visit megaphone.fm/adchoices