The mountain fortress in modern Pakistan that Alexander captured was Aornus, also spelled Aornos or Aornus. The stronghold was probably located on Pir-Sar, a dramatic mountain spur above the upper Indus in present-day Khyber Pakhtunkhwa.
Alexander besieged Aornus in 326 BCE after fighting the Assacenians. Its position threatened the Macedonian army’s supply route back toward Bactria, and ancient writers described it as so difficult to capture that even Heracles was said to have failed. The summit had springs and enough level ground for crops, so simply starving the defenders was unlikely to work.
Alexander’s engineers built an earthwork approach across a ravine, allowing troops and siege equipment to reach the rock. When the defenders began abandoning the summit, Alexander’s soldiers climbed the final rock face, reportedly using ropes. The “night scaling” detail is associated with the defenders’ retreat and the assault’s surprise character; the fortress’s name, rather than Sogdian Rock, is the canonical answer. Aornus remains difficult to identify with absolute certainty, although Pir-Sar is the leading proposal.