Most prior-service Marines may re-enlist at the grade held at the time of separation.
Non-Marine Prior Service enlist at the grade of E-2 (Private First Class), but only if they have more than 180 days (six months) of continuous active duty, and were discharged from their other service in the grade of E-2 or above.
In any event, rank cannot be worn until graduation from boot camp.
For Non-Marine Prior Service, maximum enlistment age is age 29 when current age is reduced by total active federal military service. In all cases, all prior service must be able to complete 20 years of service by age 55. No waivers are authorized.
