The standard K ration was commissioned by the U.S. Army in 1941, when they employed Dr. Ancel Keys, a University of Minnesota physiologist, to design a non-perishable emergency combat ration. The ration was intended to supply soldiers with three meals containing enough calories and nutrition to sustain combat operations for a short duration. Keys' initial menu consisted of hard biscuits, sausage, chocolate, hard candy, and a vitamin. The menu was dubbed "better than nothing" by initial test subjects, and a new menu was commissioned, eventually including more variety:
Breakfast: a canned entree such as chopped ham and eggs or veal loaf; hard biscuits; dried fruit bar or cereal bar; water purification tablets; a 4-pack of cigarettes; chewing gum; instant coffee; and sugar
Lunch: a canned entree such as processed ham and cheese; hard biscuits; malted milk tablets or caramels; sugar; salt; 4-pack of cigarettes; book of matches; chewing gum; powdered beverage packet
Dinner: canned meat such as chicken paté or pork luncheon meat; carrot and apple; hard biscuits; two-ounce D ration emergency chocolate bar; commercial sweet chocolate bar; packet of toilet paper tissues; 4-pack of cigarettes; chewing gum; bouillon soup cube or powder packet
Tests were conducted in Panama over rolling hills at a light march pace in 1942, and after three days, none of the soldiers in the test had lost significant weight. The complete daily intake of calories totaled between 2,800 and 3,000 and was recommended for only up to 15 days' use.
However, the caloric needs of men on extended marches, digging trenches, or other combat-related activities well exceed that total, especially in very hot climates such as in the Pacific Theater. Malnutrition became a factor for these men, and for those in besieged European areas where K rations were eaten for months at a time. Men in Burma lost in excess of 35 pounds during their campaigns and became less resistant to tropical diseases.
Some soldiers were able to supplement their meals with rations taken from other soldiers (German rations, in particular, were coveted because their cheese and sausage tasted better), but the pork loaf and acidic lemon power were considered completely unpalatable by many. They simply tossed the offending items, thus reducing the calories available to them.
Jungle and mountain rations were also produced, but Army supply officers hated them because their production required additional local contacts to supply fresher foods, and the expense of supplying 4,000 daily calories per man was considered too high. Both the jungle and mountain rations were cut completely in 1943 in favor of the inadequate--yet cost effective!--K rations. But that same year, the Army declared that K rations should only be used for up to five days, but by then many units were already in the field and had little access to updated replacements.
Other rations such as the C ration were deemed too unwieldy on long marches, although they were more nutritious, and the monotony of the menu caused morale problems. Accessory packs containing different flavors of water tablets, candy, and hard crackers helped, but even these improvements couldn't assuage the dullness of weeks and even months eating the same food every day.