Military personnel with sea-time experience have always been able to use their service when transitioning to the commercial maritime industry. But the process, while common, has often been complicated. The Maritime Administration (MARAD) and the US Coast Guard have long been working on simplifying the crossover. While a sea-day in the military may not always be exactly equivalent to a sea-day in civilian service, and while service in certain military capacities may not translate into any equivalent sea time, much will.
Military to Mariners provides an overview to the various options available, including generic information on the the use of GI Benefits to training programs. Furthermore Chapter 2 of the Marine Safety Manual provides even more guidance on equivalencies and details the application procedure.
As the NMC site notes, military service in the Deck or Engine department may be creditable toward a Deck or Engine license. If so and how much credit will be given can only be determined after submission of a formal application to the USCG.