eli5: How did old militaries (such as ancient Rome) manage to keep fed and hydrated thousands soldiers in long military campaigns over long distance and time?

Question

eli5: How did old militaries (such as ancient Rome) manage to keep fed and hydrated thousands soldiers in long military campaigns over long distance and time?

In: 8

Answer 1

The Russians defeated Napoleon without a single direct attack. They removed food supplies along the road. Scorched earth. They picked off foraging, hunting squads. He rode in with what I think was the largest army ever. A million, and walked out with some 20 000 survivors.

You would think the Russians would have learned from their own history.