Say I am in an english army during the Hundred Years War on campaign in France.
How and what did I eat?
How did the army get the food?
Who was in charge of feeding me?
Who provided me with my arms and armor, assuming I am a regular foot soldier?
How did I get paid, how much and how frequently?
Who were my leaders at a local level?
Here are two threads about this topic with some pretty interesting looking answers:
/u/mormengil and /u/reginaldaugustus look like they provided some useful answers.
Regarding the supply of arms and armour, I dealt with this topic in this thread, and can answer any follow up questions that you have.
So one very specific answer which I've been studying for my thesis: The Mercian armies which fought against the Vikings in tenth century England were to some extent supplied from a central hub at Stafford.
Martin Carver's excavations at Stafford found that large areas of the burh or fortress there were turned over to baking loaves of bread and bannocks (like porridge bread), butchering animals and making pottery. Stafford Ware pottery is quite distinctive, and mostly constitutes bowls, cups and storage jars, and also shows up almost uniquely only in sites with a military context.
(Carver, 2010, Stafford: The Birth of a Borough, Boydell and Brewer)