For enlisted Soldiers, the time between being sworn in and Basic Training could be as short as two days, or as long as a year. It also varies on the job assignment and branch of service. For Army Officers, the time to join depends on the path you choose. If you choose Army Reserve Officers’ Training Corps (ROTC) or the U.S. Military Academy (USMA), you’ll become an Officer after completing four years of college. If you’re going through Officer Candidate School (OCS) or direct commission, the time it will take to join will depend on when you finish your four-year degree and complete specific courses and certifications related to your branch.