That stuff is like 1/2 oil. I would probably not be able to eat more then a slice without dying of heartburn.
I think Mainstay/Datrex type rations are better, since they are made with wheat and are not nearly as fatty.
The nutritional information on the pack gave the following;
Per 100 grams
Energy 2247 kJ / 539 kcal
Protein - 14g
Carbohydrate - 42g
Fat - 35g
The Mainstay ration nutritional information is slightly more difficult to read but for the following 216 (250 gram ??) / 1200 kcal pack
Protein - 4g
Carbohydrate - 57g
Fat - 29g
These figures are for per 100 grams
So the fat content of the Halva is only slightly more than the Mainstay ration. The Mainstay ration of course has a much longer shelf life and is said to be non-Thirst Provoking.
Perhaps the Mainstay ration would be be suited to hotter environments where water may be at a premium and the Halva suited for colder wetter environments where a slightly higher fat and protein content is acceptable.
Then of course there is the famous
Kendal Mint Cake.