Medic, Corpsman and Aidman are terms used during the Korean War to refer to enlisted men in the US Army who were trained and employed to provide medical care to troops. Although the term "corpsman" is now used mainly to refer to enlisted Navy medical personnel, the US Army did have an MOS for Medical Corpsman during World War 2 and the Korean War. Therefore when M*A*S*H uses the term "corpsman" frequently in dialogue and credits, this is historically accurate and not a goof.
The US Army medical service had several different categories of medically trained enlisted men during the Korean War. Besides medical corpsmen (MOS 5657), there were also aidman (MOS 3666), and then technicians in specific areas such as X-ray technicians (MOS 3264), pharmacy technicians (MOS 3859) and so on. All of these could be referred to informally as medics. The difference lay in the amount of training given and the kinds of tasks they were assigned to.
Recruits were first given 8 weeks of basic combat training. After this, they would proceed to specialised training in their assigned MOS such as infantrymen, artillerymen and so on. Those assigned to the medical service would go on to advanced medical training. After 2 weeks of advanced training, the medical trainees would be split into three groups. Those with relevant civilian experience or qualifications go directly to assignments or else be trained as in Medical Field Service School as technicians. Of the remaining trainees, those with better educational and physical attributes would be trained as aidman while the rest would be trained as corpsman. Training in the US took place at Fort Sam Houston. The Far East Command also ran courses at the Far East Command Medical Service Specialist School at Shinodayama, Osaka, and, after 1952, at Eta Jima.
Corpsman had basic first-aid training but were mainly employed as litter bearers, ambulance drivers and hospital orderlies. Aidmen had more medical training and would accompany fighting troops. Each company would have four aidmen who would follow the troops into the frontline. During combat, the first person to tend to a wounded soldier would typically be the company aidman. Aidmen would also be stationed at the battalion aid station and other medical facilities to assist doctors.
In practice, the lines between the categories of personnel became blurred. It was common for medics to be taught on-the-job to do more than they were originally trained for. It was also common, in cases of urgent need, for units to send riflemen to a battalion aid station for some quick medical training and then deploy them as aidmen.
Corpsmen in MASHEdit
Corpsmen are frequently seen in the 4077th MASH especially in when they are receiving wounded from helicopters or during the outdoor triage scenes. The most recognizable corpsman would be Klinger. He is frequently seen carrying litters, driving ambulances and litter jeeps and performing orderly duties in the the hospital. In Season 3 "Aid Station", we can see that he has very little training in the skills needed to directly tend to a patient and Hawkeye has to teach him what to do. By Season 7 "They Call the Wind Korea", this has improved and he can assist Winchester, fetching and improvising surgical implements. In Season 7 "Point of View" we see Klinger in charge of the X-ray. This would normally be the role of the X-ray technician but Klinger probably received some on-the-job training for this.
Aidmen in MASHEdit
Aidmen are a less common sight in the MASH camp as most of them would be on the frontline tending to troops directly but they are seen when they accompany wounded on ambulances back to the MASH, at aid stations or combat scenes. In Season 3 "White Gold", Corporal Perkins is a medic with the 415th Infantry Regiment tries to steal penicillin from the MASH because the frontline units were not getting enough of it to treat their wounded. In Season 5 "Post Op", Corporal Moody accompanies wounded back to the MASH on board an ambulance. In Season 7 "The Billfold Syndrome", Sergeant Jerry Nielsen is an aidman who tends to wounded in combat and then loses his memory and cannot remember who he is.
Technicians in MASHEdit
Technicians should be a common sight in the MASH camp but very few are actually seen. In Season 6 "Major Topper", Sergeant Glassberg is probably the pharmacy technician. He is on duty in the pharmacy when Hawkeye and B.J. come in to make placebos.