https://en.wikipedia.org/wiki/The_General_series

After the apocalyptic civil war in the Terran Federation destroys civilization across the galaxy, a young man activates a supercomputer hidden deep beneath some ruins, and goes forth to unite world world.

There are some followup stories and series, I wrote this up in a similar vein (The original was Belisarius and Justinian's Conquests, others involved the Fall of the Roman Republic, World War II, and Egypt), with it's theme being the Alexandrian conquest of the Near East.

Started it a few years ago, finished today because why not.