So Alexander managed to take an army of Greeks from Greece to India, on foot, all while fighting numerous battles. My question is, what did his soldiers eat? where did the get / how did they upkeep their equipment?
Alexander conquered territories that had strong bureaucracies with good supplies of food. The Achaemenid empire was one of the best empires of their time with regards to logistics and Alexander was able to adopt that system. This carried on with strong supply trains into India but by the time they reached the latest part of their conquests the supply lines were very tight and not as effective. In fact on the return journey, Alexander had his troops march an absurd route and he lost as many men as he did in the entire campaign in part because of poor supply lines.