This Olive-Drab.com section has separate pages covering the military food supply, combat rations, ranging from the canned rations of World War II, Korea and Vietnam to the modern Meals, Ready to Eat (MRE) and HooAH! Bar:
Field food distribution point for Lt. General Walter Kreuger's Third Army,
during Louisiana Maneuvers, 1942.
There are many fine websites that have additional information on this
topic, too many to list here and too many to keep up with as they come and go.
Use this Google web search form to get an up to date report of what's out there.
For good results, try entering this: military rations mre. Then click the Search button.