Right now (2005), the Air Force is the hardest active duty service for prior service to enlist, and the Army is the easiest. The Marine Corps and the Navy are accepting prior service, but not in large numbers. The Air Force has accepted only a handful of prior service applicants during the past two years -- only those who are already qualified in extremely hard-to-fill jobs, such as Pararescue, Combat Controller, or Linguist.
So, in order for a prior-service to enlist, the service must be under their goal for re-enlistments. For the past few years, re-enlistment rates have been right on target for all of the services. With the exception of the Army, waiting times of a year or more for prior service to enlist are not uncommon.
Because there is usually many more prior-service who want to enlist than there are available positions, some of the services do not even give "enlistment credit" for recruiters to enlist prior service. Some of the services do give "enlistment credit," but not until the applicant actually goes on active duty (which might take a year or more). Add this to the fact that prior service enlistments require more "paperwork," and effort by the recruiter, it's understandable that many recruiters would rather spend their valuable time working with non-prior-service recruits.
More than one recruiter has told me, "if a prior service wants to enlist, they can expect to do much of the running around to gather necessary records and documents, themselves. Don't expect the recruiter to drop everything to get a copy of medical records or criminal records for prior-service." So, you might have to shop around awhile to find a recruiter who is willing to work with you.
In most cases, prior service candidates must enlist in the military job they had at the time of separation, unless the service declares there is no need for that job. Only then can the member elect to enlist into a different job. Additionally, in many cases, if the member had a military job (MOS/AFSC/Rating) in one service that directly cross-relates ( see chart) to a job in the service they want to join, and if that service has a shortage in that job, the applicant is required to enlist in that particular job. In other words, if you were an MP in the Army, and you wish to join the Air Force, and the Air Force has a current shortage of Security Forces personnel, you would be required to enlist as an Air Force Security Forces troop. Only if you held a job that doesn't directly cross-relate to a job in the service you are joining, or if the service doesn't have a shortage in that job, would you be allowed to re-train into a different job.
Whether or not you have to go through boot camp varies in each of the services. The Marines pretty much require all prior-service from other services to go through Marine Boot Camp. In the Army, former members of other services (except the Marine Corps), are required to attend the four-week Warrior Transition Course at Fort Bliss, Texas. Former Solders and Marines who have a break in service of more than three years must also attend this course. For the purpose of this section, for soldiers and Marines who separate, break in service starts after Military Service Obligation (MSO) is completed or when a member (regardless of service) is no longer a member of a reserve component (including the IRR).
For the Navy, the boot camp decision is made individually, after examining the person's military experience. In the Air Force, few prior-service must go through Air Force basic. Instead, they attend a 10-day Air Force familiarization course at Lackland Air Force Base.
For the Coast Guard, non-Coast Guard veterans with more than two years of active duty service attend a 30 day basic called "Pit Stop." All others attend the full-Coast Guard Basic Training.
Whether or not a prior service enlistee retains the same rank/rate they had at the time of discharge, varies with each of the services.
Below are the general rules about retaining rank: