How do you get back in the military?

If you are prior service (already served in a branch of military), locate your DD 214's, you 201 files and any paperwork you have from you time in service, contact a local recruiter and they will start the process of enlistment. Keep in mind depending on how long you have been out of service you may have to redo your physical at MEPS, you job availability or selection will be cut down significantly, you may have to take a reduction in rank and you just may not be able to get back in. There are a lot of different factors that come in to play for a Prior Service applicant than there are for new recruits.