The following link makes comment (amongst other things) of just how even the terrain of Afghanistan works against an invader. Alexander the Great is said to have lost more soldiers just crossing Afghanistan from south to north than he ever lost in any battle that he fought.
His Afghanistan campaign also saw the beginning of the physical and moral degradation of the young king.
https://warfarehistorynetwork.com/2015/11/11/alexander-the-great-in-afghanistan/