Some corrections to what you posted: You can enlist at age 17 with your parents' permission; you can also be naturalized at age 17 if you are in the military (active or Selected Reserve). If you are discharged early, DHS makes the decision whether to take away your US citizenship--not the Army. You must serve five (5) years honorably in order to keep your citizenship--that's in the statute. MAVNI only requires four years of active service, but keeping your citizenship requires five years of honorable service in any component (active or Reserve). So if you don't trust USCIS or DHS to make the right decision, joining the military may not be for you.