Having soldiers handle logistics for themselves existed for an extended period, but had major problems. In practice this often looked like soldiers foraging/looting for food, which can work in the short term but has major problems. Foraging parties are vulnerable to attacks, can provoke the populace against you, and eventually deplete easily available resources.
An army relying on foraging/looting could (and some did!) find itself unable to stay in one place for too long as a result of these dynamics, which would be awkward in a siege or similar (sure, you can go plunder the countryside around the castle, but you might run out of stuff to plunder before the guys inside the fort run out of their food stockpiles...). Similarly, if you’re besieging the enemy but your guys won’t be able to scavenge for food effectively once winter arrives, you might be forced to withdraw prematurely.
Having soldiers handle logistics for themselves existed for an extended period, but had major problems. In practice this often looked like soldiers foraging/looting for food, which can work in the short term but has major problems. Foraging parties are vulnerable to attacks, can provoke the populace against you, and eventually deplete easily available resources.
An army relying on foraging/looting could (and some did!) find itself unable to stay in one place for too long as a result of these dynamics, which would be awkward in a siege or similar (sure, you can go plunder the countryside around the castle, but you might run out of stuff to plunder before the guys inside the fort run out of their food stockpiles...). Similarly, if you’re besieging the enemy but your guys won’t be able to scavenge for food effectively once winter arrives, you might be forced to withdraw prematurely.