Donald Engels wrote what is kinda the definitive work on this subject, and I highly recommend it, as it's a fascinating subject, because the accomplishment of Alexander the Great cannot be overstated. (1)
There were large bodies of men not well disposed to this young Greek traipsing through their territories with his army, but more importantly there were vast swathes of often quite hostile landscape across which Alexander had to move his men. Alexander was able to meet these strategic, tactical, and logistical concerns with seeming ease. Much ink has been spilled over the millennia concerning Alexander’s strategic and tactical genius, less so his ability as a logistical commander, and that is a damn shame because he was a genius.
First and foremost was the preparation that took place under his father, Philip. Key among these preparations was the organization of the Macedonian Army into the most efficient campaigning force the Mediterranean had ever seen. A key part of this plan was expanding the prestige of the infantry unit, which would prove so essential to his battle plans. Philip accomplished this by making the soldiers of the infantry loyal to him personally, in a shift away from their home region or city. These ‘foot companions’ enjoyed the prestige of being considered directly connected to their king just as the aristocracy already had been for generations. (2)
By making the men individually and as a unit loyal to their commander and king, Philip was aiming to wage war in a way that Greeks had not done before. Greek discipline operated in a way that might be alien to our modern idea of discipline, which places an emphasis on following orders.
the main focus of Greek discipline was on the opinion of your fellow soldier-citizens, and in trials for failure to obey orders, the key concern was whether the soldier-citizen had disobeyed orders for reasons of cowardice. Cowardice was the principal concern. Philip’s reforms to the Macedonian military are key to understanding the way he changed the army’s discipline. The existing institution of the Cavalry Companions, consisting of the elite of the Macedonian state, had enjoyed extensive freedom to question their commander and king bluntly. By expanding this and other privileges to include the infantry, Philip was also able to induce a constriction on the freedom of all his soldiers to disobey. The soldiers, having theoretically gained the right to question their king, gave up their traditional freedom to disobey. Effectively, the old nobility were given new obligations, and a new nobility was recruited on the basis of professionalism, meritocracy, and most important of all - loyalty.
It would not have been difficult to impress upon the men that loyalty meant obedience, by demonstrating that the rewards for loyalty flowed to those most obedient to commands. Therefore, reforms such as Philip’s forbidding of wagons and restricting the number of servants each fighting man was permitted created a situation wherein the armed force was able to field four combatants for every one servant. The men accepted such restrictions, and requirements to carry their own supplies, because to do so meant they would be rewarded. (3)
1) Donald Engels, "Alexander the Great and the Logistics of the Macedonian Army." University of California Press, 1978
2) Bosworth, A.B. "ΑΣΘΕΤΑΙΡΟΙ." The Classical Quarterly 23, no. 2 (November 1973): 245-253
3) John Keegan, "The Mask of Command." Penguin, 1987
) Donald Engels, "Alexander the Great and the Logistics of the Macedonian Army." University of California Press, 1978