Commissioned officers qualified to contribute to an activity of another uniformed service may apply for interservice transfer without interruption in their service career. Interservice transfers are intended for use primarily in technical fields to permit full use of specialists, but will not be restricted to technical specialists. Interservice transfers may be used to help fulfill authorized strength requirements in competitive categories, designators, occupational fields, military occupational specialties, and other authorized officer specialties. They may not be made from shortage specialties.
SECNAVINST 1000.7G and MILPERSMAN 1300-081 are the governing instructions for interservice transfer requests.
U.S. ARMY INTERSERVICE
Officers interested in an IST may wish to consider the ARMY INTERSERVICE TRANSFER program. This link will take you to the US Army's Blue to Green web page. An interservice transfer is required to partake in the Blue to Green program.