EARLY in the war in Afghanistan, among the international troops who mingle at Bagram Air Base, a single French combat ration (cassoulet, perhaps, with deer pâté and nougat) could be traded for at least five American Meals Ready to Eat, better known as M.R.E.’s.

Recently though, the barter values have changed.

A fellow journalist who just got back from an embed with the French told me that today they look forward to visiting the Americans for a meal. American rations — hamburgers, chili, peanut butter, candy — they say, are “fun.”

Each year, among the countries with troops in Afghanistan — the current number is 47 — tens of millions of dollars are spent researching how to fit the most calories, nutrition and either comfort or fun into a small, light package. The menus and accompaniments are intended not just to nourish but also to remind the soldier of home. Some include branded comfort foods — Australians get a dark-brown spreadable yeast-paste treat called Vegemite, for example — while others get national staples like liverwurst (Germany), or lamb curry (Britain’s current culinary obsession).

Some of the contents are practical. Italians get three disposable toothbrushes per day of combat. Americans get pound cake, which military folklore says reduces the need for toilet breaks.