They briefly convinced the Army/Marines that they could make electric/hydraulic mules to assist soldiers in carrying their gear in terrain without roads. But they were too loud - at that point, might as well insert troops/material by helicopter or use horses/mules.
http://spectrum.ieee.org/automaton/robotics/military-robots/...
Seems like a classic case of poorly chosen requirements. Someone specced a robotic mule with such-and-such range, carrying capacity and features, and forgot to add 'also must be quieter than weed whacker'.
