A battalion aid station is a temporary medical facility set up within an battalion for the immediate treatment of sick or wounded troops. In the U.S. Army, a battalion aid station is an Echelon I facility along the chain of casualty evacuation, in other words, it would be the first medical facility a wounded soldier would be brought to for treatment. As such, the aid station would usually be only several hundred yards behind the front, set up under tents or in a building of some kind. It would be within the range of enemy artillery or snipers, and would move back and forth with the fighting troops.
A wounded soldier would first be treated at the point of injury by himself, his buddies or by the company aidmen (each company of troops had three or four). Field dressings and sulfa powder would be applied and sulfa tablets taken if possible - every soldier carried a quantity of these. The wounded soldier would then be taken by foot, or by litter bearers if he couldn't walk, to a battalion aid station.
A Battalion aid station in Europe during WW2. Doctors and medics prepare casualties for evacuation.
A battalion aid station was usually headed by the battalion surgeon (a doctor of the rank of captain) and assisted by a lieutenant from the Medical Service Corps (an administrator who also has first aid training). There would also be 6-8 aidmen/corpsmen. The term battalion surgeon is traditional - typically the doctor in a battalion aid station would be a generalist without specific surgical training. His role was as a general practitioner in contrast to the specialist surgeons of a MASH. A battalion aid station handled sick call for the unit and gave immediate first aid to wounded. Bandages would be adjusted, splints applied, morphine and plasma administered. Those needing further treatment would be sent on to Echelon II facilities - a divisional clearing station or a MASH. As such, the role of a battalion aid station was to stabilize and evacuate casualties rather than provide detailed treatment.
Battalion aid station in MASH[]
Battalion aid stations form the stage immediately before a MASH in the chain of casualty evacuation and as such show up frequently in episodes of M*A*S*H.
In Season 3 "Aid Station", Hawkeye, Margaret and Klinger are sent to reinforce the personnel at an aid station because the battalion surgeon had been killed. In Season 4 "Der Tag", Hawkeye and B.J. turn up at a battalion aid station to collect an unconscious Frank who had ended up there because he had passed out in an ambulance. While there, they assist in treating the wounded. B.J. asks for a suture setup to perform some surgery but Capt. Saunders, the battalion surgeon, advises him that they are at an aid station, not a MASH, and there wasn't time for detailed surgery - they had to focus on stabilizing the patient and evacuating him.
In Season 4 "Smilin' Jack", Lieutenant Jack Mitchell wants to break the chopper pilot of the Year record and so flies to an aid station to lift four wounded personnel at one go.
In Season 5 "End Run", Sergeant Billy Tyler is wounded and brought to an aid station where because of his serious injuries, the battalion surgeon calls for a chopper to bring him directly to the 4077th MASH. The same happens in Season 7 "Point of View" where an injured Private Rich is evacuated from an aid station by chopper.
A Battalion aid station in M*A*S*H from the Season 5 episode "End Run". Notice the similarity to the real-life photo above. In the foreground medics prepare to load the casualty into the ambulance for evacuation. In the background, the battalion surgeon is on the radio calling in a chopper medevac for Sgt. Billy Tyler who is on the stretcher next to him.