United States
Navy specialty code for Hospital
Corpsman. It signifies that a member has been trained in combat medicine and is qualified to travel in the field with the United States
Marine Corps as medical support.
The Marines do not have any medical personnel of their own, so they rely upon Naval medical personnel.
Corpsmen are usually the first to respond to injury during manuevers (or in combat) for the Marines.
In more realistic war movies starring Marines, the cry "Corpsman Up!" would be more accurate than "Medic!" Experience has also shown me that most 8404 Corpsmen are called "doc" by the Marines they serve with.
The Corpsman are also usually trusted with far more than just the health of the group. Many become the de facto moderating force amongst smaller groups of Marines and will often become very close friends with most of the Marines they serve with.