Literally hospitals on wheels, the large, sophisticated MASH trucks are able to supply wounded MechWarriors with the finest possible medical care.
         Every well-equipped regiment is assigned at least one Mobile Army Surgical Hospital.   The vehicle needs to station itself as close as possible to the action, perhaps in an open field near several roads.   The MASH then unfolds itself and powers up its medical equipment.   In the meantime, army engineers devise a landing pad to handle the air vehicles that will ferry the wounded from the front line to the rear, where evacuation offworld can be accomplished if necessary.   Though only lightly armed, the MASH is rarely attacked, for it provides medical services to the wounded of both sides of the battle.

         The MASH is capable of supplying the highest level of hospital care.   Often manned by the best civilian surgeons, its facilities permit even the most delicate surgeries, as long as there is a steady source of medical supplies and relative calm in which to operate.
         Having chosen their field location, the MASH team unhitches the vehicle's right side, which is hinged along the bottom edge.   The whole panel is then lowered to the level of the truck's floor.   This becomes an extension of the hospital area, and is fixed into place with strong legs and supports bracing it from underneath.   Temporary walls and a roof are erected around the extension, connecting it to the truck's interior.   Now the expanded interior can be made sterile, awaiting the arrival of the wounded.
         Using materials unloaded from the trucks, several other temporary structures are also built.   One group of buildings is for triage, the screening of the wounded to determine the severity of their injuries.   Another group of buildings contains the medical diagnostic equipment, such as body fluid analyzers, X-ray machines, and neuroscanners, which are all hooked up to the MASH truck for power.
           The next group of buildings houses recuperating patients.   They will either recover here and then return to battle, or they will be sent offworld for further treatment.
         The interior of the MASH is a high-tech affair.   Entering through one set of wide doors, the patient is taken to a table to be prepared for surgery.   In the meantime, one of the five team doctors is at a terminal accessing the results of medical tests on the patient.   From the results, the MASH's computer suggests a plan of action to the surgeon.
           Having been prepped, the patient is brought to the surgeon and placed on the automated table, whose robot arms administer anesthesia.   From there, the surgeon takes over.   When he wants a surgical instrument such as a laser scalpel, the table automatically dispenses it via a group of robot hands stationed over the tray of sterile equipment.
         Depending on the situation, either the triage officer or the computer compiles continuos reports on the patient's condition, which the surgeon receives simultaneously through a small earphone.   When he needs to consult a test result or an X-ray, it immediately appears on a nearby data screen.   In an emergency, such as sudden heart failure or a seizure, the surgeon can take control of one of the automated table's many mechanical hands.   The machine understands a wide variety of surgical maneuvers and can greatly aid the beleaguered surgeon.      
         If the patient is slipping away too fast, the surgeon can initiate the emergency freeze procedure.   A large, clean cover descends onto the table, turning it into a large, air-tight tube containing the patient.   Once in place, the tube's temperature is lowered by flooding the interior with a clear, oxygen-rich liquid.   The surgeon then places his hands through sleeves leading into the air-tight area and continues operating, with the table providing instruments from underneath its cover.
         Once the operation is complete, the surgeon enters data into the computer on post-op care, medication needed, and any other notes.   This information is available to the nurses in the post-op ward, who will add their own observations to the patient's record.
         If a sudden change in the fortunes of war forces the MASH to move suddenly, it can disassemble its temporary structures and send patients on in ambulances, all in less than four hours.   Drugs and medical equipment are loaded back onto the MASH, with supply trucks carting away the remaining non-medical supplies.
         As the surgery is prepared to move, only one of the five operating theaters is stripped down and stowed.   The truck's right wall is lifted back up, then reattached to the truck so that the rear of the MASH can hold six of the most seriously injured patients.   Even moving at high speeds, some surgery can be performed in the one operating theater.
         The MASH is lightly armed, more to discourage thieves than to inflict major damage.   Mercenaries are particularly anxious to acquire a MASH, which they may try to steal by killing the driver or by blockading the road on which it is traveling.   This has happened only rarely, and so some MASH doctors have removed the truck's weapons on ethical grounds.   As smoke and barrages of fire often obscures the large red cross painted on the vehicle's sensitive equipment, the sides of the truck are fairly well-armored.

         The first modern MASH units were an immediate success, improving a wounded soldier's chances of surviving a serious injury by over 300 percent.   With their fast speeds, the MASH trucks made it easy to keep high-quality medical care quite close to the front.

         While each of the Successor States built their own MASH trucks, their exteriors are very similar.   Smaller models have only three operating theaters, while the White Whales of the Free Worlds League can have up to seven surgeons operating at the same time.
         Because of the dwindling supply of fusion engines and the increased military demand of the remaining vehicles, some MASH trucks have converted to internal combustion engines.   This greatly reduces the efficiency of the MASH, as at least one and sometimes two operating theaters must be removed.   Nor can these ICE models power as many diagnostic test machines as the fusion-powered models.

         The first MASH units appeared during the Korean War in Earth's ancient history.   By the end of the period known as the Exodus, MASH units had to be assembled by fleets of trucks and engineers, and it took days to erect or remove them.   Because of that time factor, many MASH units were captured, a very costly loss.
         The idea of installing certain diagnostic equipment on trucks and vans to allow for quick retreats was gradually put into practice.   First came a portable power supply, then the diagnostic equipment, then whole trucks employed as mobile wards.   The first mobile surgery theater was employed in the opening battles of the Age of War, evolving quickly into the MASH unit known today.