 Alexander eventually found a path to the rear of the Persians from the captured prisoners of war or a local shepherd, defeating the Persians and capturing Persepolis.The Persian Empire suffered a series of defeats against the Macedonian forces at Granicus (334 BC), Issus (333 BC) and Gaugamela (331 BC), and by the end of 331 BC Alexander had advanced to Babylon and Susa.A Royal Road connected Susa (the first Persian capital city in Elam) with the more eastern capitals of Persepolis and Pasargadae in Persis, and was the natural venue for Alexander's continued campaign.