Enrolling in the ROTC Basic Course (the first two years of college) does not obligate you to serve unless you receive a scholarship. If you received a four-year ROTC scholarship, you must agree to serve four years full-time as an Army Officer after you graduate and then either extend your contract for your more years or serve four more years with the Individual Ready Reserve (IRR) where you'll return to civilian life but need to be ready to help in a national emergency. If you received a three-year or two-year ROTC scholarship, you must agree to serve four years full-time as Army Officer after you graduate.