How Did Alexander the Great Conquer the Persian Empire?

Alexander the Great conquered the Persians using the roads that they had built. Unfortunately this was not a good thing for the Persians because although it did help to establish and put in place a male service, a postal service as well as control over a large territory but also brought down the Persian Empire. The Incas were around from about 1438 AD so they're more modern to 1532 AD. Their power base is what would be modern day Peru and a little bit into Ecuador and Chile.