Ration D was adopted as an emergency ration on November 9, 1938. On October 17, 1939, this emergency ration was officially standardized as Field Ration D of the U.S. Army.
Ration D is a 4-ounce bar of chocolate with the addition of a large amount of sugar, milk powder, cocoa butter and oatmeal.
A high percentage of dry substances in the composition makes the bar harder than ordinary chocolate. During the development, this was considered as a positive property, because due to the low taste qualities, the soldiers did not use it as candy immediately after receiving it, but stored it until an emergency situation arose.
A bar of chocolate was intended to replace only one missed meal, so three bars make up one complete diet for three meals. A full diet of three bars contained 1800 calories.
There were three types of tiles: 4 oz, 2 oz and 1 oz.
Early instructions provided for wrapping the diet with aluminum foil, followed by wrapping it in parchment paper.
Since February 1942, the ration was packed in a cellophane bag, which was inserted into a cardboard box.