Michael Niedermayer used to fly drones for the U.S. Army and the Central Intelligence Agency, gathering real-time, life-and-death intelligence on battlefields in Iraq. Now he pilots delivery robots for a San Francisco Bay Area startup that wants to disrupt burrito delivery.

Postmates, which in mid-August received a permit to operate its Serve delivery robot in San Francisco and is already testing it for food delivery in Los Angeles, employs a growing team of “pilots” to remotely oversee, and at times steer, these four-wheeled food ferries.

“We will probably see a drastic increase in our workforce over the next five years,” says Postmates Chief Executive Bastian Lehmann.

Disrupting “last-mile” delivery—historically the domain of box trucks, bike couriers and personal vehicles—“felt like a great fit for my military background,” says Mr. Niedermayer.