Joshua Stein, general counsel for San Francisco-based human resources software company Zenefits, is half-coach, half-soldier. Literally.

Stein joined the Army in 1992, fresh out of college, looking forward to a 20-year career complete with what gets shown in commercials—“jumping out of airplanes, running around in the woods, firing off weapons systems,” he said. But a drawn-down army, lessened in ranks following the end of the Cold War, Stein said, proved less exciting.