the Great]] invades northern [[India]]. Recrossing the [[Hindu Kush]], Alexander divides his forces. Half the army with the baggage under [[Hephaestion]] and [[Perdiccas]], both cavalry commanders, are sent through the [[Khyber Pass]], while Alexander leads the rest, together with his siege train, through the hills to the north. His advance through [[Swat (Pakistan)|Swat]] and [[Gandhara]] is marked by the storming of the almost impregnable pinnacle of [[Aornos ]], a few miles west of the [[Indus]].
The relations between Alexander and [[Aristotle]] are embittered by the execution of Aristotle's nephew, the historian [[Callisthenes]] of [[Olynthus]], who is charged with [[ treason]]. Callisthenes has been accompanying Alexander to write a chronicle of the campaign.