The Mobile Army Surgical Hospital, or MASH as it quickly became known, was a new kind of organization, announced on 23 August 1945, at the very end of World War II. The MASH was intended to bring emergency lifesaving surgery closer to critically wounded casualties. The MASH was to be truly mobile, fully staffed with surgical and medical personnel, and equipped to provide definitive, life-saving surgery, to make the patient transportable to rear medical facilities, and to provide post-operative care for non-transportable patients.Once a soldier got to a MASH unit he had a 97% chance of survival.

Standards for a MASH required that it was disassembled, loaded onto vehicles, and ready to depart on six hours notice. After arrival at its new destination, it was operational within four hours. Each MASH operated five surgical tables in a shift with a highly organized system of managing shock patients. An ambulance platoon was attached to each MASH to facilitate the rapid evacuation when post-operative recovery was complete, also there were four helecopters in each mash for faster movement of patients.
The Mobile Army Surgical Hospital (MASH) concept was firmly established by its success in Korea and MASH units continued to serve, deployed to Vietnam, the 1991 Gulf War, and the conflicts in Iraq and Afghanistan in the 2000s. At the same time, after a lag of 15-20 years, the Korean War MASH success in trauma management through helicopter evacuation, enlisted medics (para-medics), and advanced methods in the treatment of shock became the model for civilian urban trauma centers. The MASH-developed doctrine became the standard of practice in the U.S. and the rest of the developed world.

Since the mid-1990s MASH units have been decommissioned one by one, converted into facilities that better meet the changing demands of combat. In 1997, the last MASH unit in South Korea was decommissioned. In October 2006, the 212th Mobile Army Surgical Hospital (the most decorated Army tactical hospital) became the 212th Combat Support Hospital, part of the Department of Defense’s transformation to brigade combat teams. The 212th MASH's last deployment was to Pakistan to support the 2005 Kashmir earthquake relief operations. Its equipment was left there, donated to Pakistan.
With the last MASH gone, its role has been superseded by the Combat Support Hospital (CSH), smaller casualty surgical hospitals intended to be deployed even closer to the front lines than the MASH.