The Mountain Ration (or "M-Ration") was a United States military ration developed for use by U.S. troops operating in high-altitude or mountainous regions of the European theatre of World War II. Origin, development, and use The components of what would become the Mountain ration were developed in 1941–42 by U.S. Army officers in experimental mountain warfare companies, largely consisting of former ski instructors, forest rangers, and other experienced alpine travelers. Based on their recommendations, the Mountain ration was finalized and packaged for use by mountain and alpine troops by personnel at the Quartermaster Corps' Subsistence Research Laboratory in Chicago, Illinois. In order to make the rations suitable for high-altitude climates, the Mountain ration was designed as a specialized compact ration that was easier to prepare in high-altitude environments, have adequate roughage, and enough bulk and quantity when heated to satisfy four men in one day at high altitude, weigh less than , and contain a total of per man per day. The ration was formally adopted in November 1942. The Mountain ration was produced from 1942 to 1943, and issued to soldiers of several elite U.S. and British Commonwealth forces then in training for alpine or winter combat, especially the 10th Mountain Division, and the First Special Service Force. As packaged, the Mountain ration was sized to serve four men for one day (three meals per man). It was normally prepared at the platoon or squad level, though 10th Division troopers were also taught to prepare it individually. The 1st Special Service Force first tried out the Mountain ration on November 28, 1942, during a training patrol to MacDonald Pass, Montana: "At 1400 hours all company commanders and one other officer from each company and a few others left by truck for MacDonald Pass to try living under winter conditions and try a new mountain ration ... On arrival at the selected spot the party broke up into groups of four and built shelters and fires of many different types. The Mountain ration, which comes in four varieties, is packed in boxes, each box containing the rations of 4 men for 3 meals, this proved to be more than the average man could eat. They included powdered soup and milk, canned meat and butter, cereal, chocolate, biscuits, compressed fruits, sugar, tea and coffee and powdered lemon." Because of its generous portions, specialization, and significantly higher cost, the Mountain ration was