Never had bully beef, but I think a thing we had here called Camp Pie was its son. Mostly sawdust held together by fat, some of it from animals. Very popular in Scout camps I attended as a kid.
I had a great idea years ago for a weekend lunch for my kids and got a tin of this vileness and sliced it and fried it, because it used to taste alright fried in Scout camps and frying got rid of some of the fat so you could fry the onions and tomatoes without adding any fat to the pan.
My brilliant idea resulted in two kids rejecting it on the first bite and me on my first bite agreeing with them.
I don’t know how we ever ate it, but it was common fare hot or cold when I was a kid. So were things like mutton and tripe and lamb brains and kidney and lamb liver, most of which would make me vomit now and a few went close then, although a properly done bit of lamb liver (lamb’s fry) and bacon under gravy with bubble and squeak (sort of a vegetable hash brown, which stands in the same realtionship to McDonalds’ hash browns as McDonalds’ products do to food) is still alright if you can find someone who knows how to cook it properly.
Where this relates to WWII is that, in Oz at least, people generally were used to much stronger and gamier flavours than we are now.
When I was a kid a lot of stuff was fried in beef dripping (fat). Like most people we used to have some enamelled tin bowls that we poured fat off mutton chops and anything else into. It started with a couple of inches of water in it and the fat congealed on top while the debris fell into the water, so the fat was clean. Then the fat was used for cooking later.
A lot of people here in the 1930s Depression thought bread and dripping, usually bread fried in dripping, was a bit of a luxury. Just starch and fat, but it filled you up. Just like bully beef and biscuits.
When I was a kid in the 1950s, chicken was a luxury for Christmas and other special occasions. Mutton or lamb were the main meat dishes, roasted, fried, or grilled, with beef occasionally. Every meat dish was served with vegetables which were boiled until they lost their colour and became mushy, which we thought of as ‘cooked’.
Bully beef probably wasn’t quite so bad for a lot of Aussies used to a very different diet and range of tastes to nowadays.