From Susa the conqueror moved on to Persepolis, the great Persian capital. On his march he had to pass through a defile of the mountains. The mountaineers had been accustomed to exact tribute here of all who passed, having a sort of right, derived from ancient usage, to the payment of a toll. They sent to Alexander when they heard that he was approaching, and informed him that he could not pass with his army without paying the customary toll. Alexander sent back word that he would meet them at the pass, and give them _their due_.