Well, most medieval armies would count on being able to live off the land as they go, requisitioning farms for example. Rations would be things like cured meat and heavily salted fish, food that can last for a long time without a fridge.
Hey, Quickleaf, I really like the work you're doing on this conversion. I'm soon going to be running an Arabian Nights campaign that's basically Al-Qadim by a different name, and I'd be keen to do some playtesting.