Alexander the Great: How did he reinforce his army?

I was watching a video on the exploits of Alexander the Great and I wondered how he managed to go from battle to battle and not run out of steam.

I get these battles were months apart but still…I thought part of the strength of Alexander’s army is they were professional (well trained and not mere conscripts).

As Alexander went from battle to battle he lost lots of his own army even as they won. So, they would need reinforcements and I doubt conscripts picked-up as they went would suffice. But Alexander easily got over 1,000 miles from home in his adventures. Back in those days that’d be a two month walk (give or take) for soldiers from home to catch up. Did he have a constant stream of new soldiers streaming in from behind him? How did that work?

It seems he got closer to 2,500 miles from home as the crow flies (he made it to Tajikistan and what is now Pakistan). Walking winding roads would likely make it a lot longer.

I’m no expert, but as I understand it, Alexander the Great was both reinforced by troops from Macedonia as well as experienced soldiers from the areas he conquered. Apparently this mix of Macedonian and Asian soldiers contributed to a rift between him and many of his veterans and inner circle.

Keep in mind, Alexander didn’t just march out from Macedonia and beat armies. He founded at least 20 cities (named Alexandria) and established control over others, effectively creating a huge contiguous Hellenistic civilization.

Local recruitment.
Few locals had a great love for their Kings or High Priests, & Alexander lowered taxes & prohibited Human sacrifices in the lands he conquered.
That made him more popular than the old rulers.

Keep in mind most of his conquering expedition took place over nearly a decade. So it’s not like they were just roaming around most of the time, fighting and doing military stuff.

So it’s likely that recruits from Macedonia, Egypt, etc… probably just made their way to wherever Alexander and his units were at the time.

I’m assuming that there wasn’t something a bit more organized going on, like maybe some units were rotated in and out of garrison duty, and they’re the ones that got the recruits to replenish their ranks, and when they were rotated back in, they were ready to go, while the more depleted units were rotated out and replenished. I don’t know… but it does seem a little bit dicey that some group of young recruits from Macedonia would just be told “Go to Alexandria Arachosia (Kandahar) and meet up with the army there.” Seems a bit risky to me.

Antipatros, one of Philippe’s generals, was regent of Macedonia when Alexander was on campaign. he did a great job maintaining the greek cities in line, and fighting Thracians. He send reinforcement after Issus battle (both phalanges and mercenaries) but wasn’t thrilled by the god complex of Alexander and was on the verge of being destitute when Alexander died.
Troops and messages were traveling easily between Macedonia and Babylonia, and there was no shortage of Greeks or Macedonian willing to participate in the war.
But Alexander alienated with his eastern politic many of his men, less willing to honor a god than follow a strategist. He recruited more and more of local troops (Persian nobles in the heavy cavalry Hetairoï corps, mixing phalanges, light troops from Scythia, Arachosia,…)