Here’s a pretty interesting graphic showing the evolution of the K-Ration throughout World War II.
Right click and open image in new tab to see the whole thing.
The K-Ration was produced in Breakfast, Dinner, and Supper menus.
Originally conceived for paratroopers, it was later adopted for widespread use throughout the Army. It was only intended to be used for three to five days before troops switched to regular meals from the mess kitchens, but many troops ended up subsisting on K-Rats for weeks at a time. That was pretty problematical, because the K-Rat just didn’t have enough calories in it. Troops in combat can easily burn through 6000 calories a day, and the 3000 or so calories from a K-Rat diet would seen see signs of malnourishment spreading through a force.
Some of the menu choices might seem a bit weird, but most were generally well accepted at first. It was the monotony of having to eat K-Rats over and over that lead to a great deal of dissatisfaction with the K-Rat by the end of the war.
[I first wrote about 3000 words on all Army rations during the war, then decided it was crap, and threw this together instead.]