In the aftermath of general slaughter and arson committed by Alexander at Massaga and Ora, numerous Assakenians fled to a high fortress called Aornos (not definitely identified but somewhere between Shangla, in Swat, and the Kohistan region, both in northern Pakistan). Alexander followed close behind their heels and besieged the strategic hill-fort. The Siege of Aornos was Alexander's last siege, the climax to Alexander's career as the greatest besieger in history, according to Robin Lane Fox. The siege took place in April 326BC. It presented the last threat to Alexander's supply line, which stretched, dangerously vulnerable, over the Hindu Kush back to Balkh, though Arrian credits Alexander's heroic desire to outdo his kinsman Heracles, who allegedly had proved unable to take the place Pir-Sar, which the Greeks called Aornis. The site lies north of Attock in what is now the Punjab, Pakistan, on a strongly reinforced mountain spur above the narrow gorges in a bend of the upper Indus. Neighboring tribesmen who surrendered to Alexander offered to lead him to the best point of access.