For decades, infantry's problem with planes has been that they're hard to reach because they're far away. Anti-aircraft weapons must be used to keep bombers and fighters from striking at troops on the ground with impunity. Now, the Marine Corps is finding a challenge with a new sort of airplane: small drones, which fly close to the battlefield, but are hard for traditional anti-air weapons to detect or hit. To counter this threat, the Marines are turning to a new tool: anti-artillery radar.

When ISIS or other insurgent groups fly drones, they don't have larger plane-sized craft like Predators and Reapers. Instead, they use smaller, commercial models, adapted as remotely piloted scouts or hand-tossed reconnaissance. These drones are too small for normal plane-detecting radar to spot, but the Marines have other radars available.