So I'm writing a story where one of the side characters had a history in the military. And I was basically wanting to know what kind of time commitment they needed in order to complete their required time for the Military. It can be any branch, the one with the shortest commitment would probably be the best. The point of all of this is I wanted to make a character that is the head of security for some firm, and he has a history of being in the Military. But I wanted to make him like 25-30 years old. But if all branches of military keep you for like more than 10 years, that probably isn't that reasonable.