The US military physician assistant (PA) originated from the corpsmen and medics of the army, navy, air force, and Coast Guard. PAs have been present in every military campaign since 1980 and serve in a wide variety of medical roles. Their combat role has expanded so that in many instances the PA has replaced the physician as the front-line care provider. All have moved from warrant officer into the commissioned officer ranks, a change that has enabled them to rise into command and administrative positions. Narrowing of the pay differential between military and civilian PAs has contributed to their retention.