Bret Devereaux

Taking fortified population centers can get you supplies, but only if you storm them - which is tricky. You need to be bigger enough than the settlement that you can just quickly build a ramp and roll on in, but not so much bigger that their stored food is trivial. 9/21

Finally, you have long distance transport, which basically only works if you are on a coast line with decent harbors, or a navigable river, *and* you have the coordination to get supplies from somewhere else moved to you in quantity. 10/21

And I do mean *quantity* - back of the envelope math suggests a single Roman legion (typically a sub-unit of a larger army) might consume 8.26 tons of food per day alone, which pops up above 10 tons when you account for fodder for animals. 11/21

So this ends up being a flexible playbook of common methods. The exact playbook may vary a bit one army to the next (one huge question that makes a big difference is, 'can your army harvest and then process and then bake raw grain?' or do you need bread made for you?)...12/21

But commanders in the field are constantly shifting the balance of methods to meet their needs. Given that ancient armies don't run out of food all of the time, they are also clearly engaging in long-term planning with rule-of-thumb assumptions that are fairly reliable. 13/21

Because, to be clear, this is a setup with relatively minimal margin of error. The limits of a pre-truck army's carrying capacity means that you can't carry more than a couple weeks supplies with you, so total collapse is never more than a few weeks away. Plan carefully. 14/21

Now, for the historian, the tricky thing is that no one tells us about this playbook. Even military manuals - your Vegetius and Onasander and so on - don't go into very much detail about the specifics of how an army did its logistics. 15/21

So we're left to sketch out the playbook by seeing what armies do in the field. There's a temptation to see that all as amateur ad hockery but remember the narrow margins for error and the complexity of the calculations being made here. 16/21