Supply lines as we know them first appeared only for very large armies (Napoleon sent something like 115,000 into eastern europe, unprecedented) and consisted almost entirely food and a trivial amount of ammunition.

On the other extreme we have, say, an armored division of the US Army. Requires tons of material to keep operating every day. If it were cut off, it's pretty much up the creek without an outboard.

Don't get me wrong, the problem of acquiring food has decided more wars than the battles thereof. In fact, wars have been started simply so the army would be able to live off the enemy's land rather than have to feed it from the country's own crops. But until relatively recently, transportation and production technology were too primitive to keep an army regularly supplied from home. Napoleon had the most ungodly difficult time getting his underlings to have enough rations available to feed his men.