Was Sam in the military?

Even if we assume Sam avoids all optional combat in the game, realistically without some kind of military training in his past there's no way Sam would have been able to go toe to toe with Cliff, and survive the major boss fights. He obviously has proficiency with many types of weapon systems including heavy ordinance, which civilian gun hobbyists wouldn't. So I think it goes without saying that before Bridges and considering he was raised in a government family it only makes sense to me that Sam would have served in the military.