“Iron Rations” for the British Tommies in World War I would be carried by soldiers when they were away from regimental cooking arrangements. A good example was when the Canadian Cavalry Brigade was in almost continuous action in late March 1918. Here’s what the troopers carried with them:
- One tin of beef (“bully beef”; Frey Bentos; with an attached key for opening).
- 6 ounces or so of biscuits.
- One ounce of beef extract (eg OXO).
- One small package of tea.
- Package of salt, and perhaps sugar.
Here is a photo taken in the Fort Garry Horse Museum in Winnipeg that gives another version of iron rations:
Pretty slim pickings for active men who could be fighting, riding, or marching--or doing all three--in a day. There probably weren’t many overweight soldiers.