First established at the end of WWII, Mobile Army Surgical Hospitals (MASH) provided treatment to a wounded soldier as quickly as possible, due to their close proximity to the frontlines. The appearance of the helicopter onto battlefields reduced the time from the actual wounding to getting the wounded soldier to a doctor or surgeon to just 30 minutes, greatly increasing their chances of survival.

The term MASH has been made famous in the movie and subsequent much-loved TV series M*A*S*H which depicts life at the fictional 4077th. These, in turn, were based on the 1968 book MASH: A Novel About Three Army Doctors by Richard Hooker (pen name of real life MASH surgeon H. Richard Hornberger) based on his experiences in the 8055th MASH in the Korean War.

Rules for using MASH units in your games of Bolt Action can be found in the Bolt Action: Korea supplement.