Pir Muhammad advanced without further delay to oppose the designs of Abu Nasr Qara Yusuf and reaching a particular spot without confrontation he became aware that a detachment of the enemy sent forward by the Kara Koyunlu chief to explore and scour the country had taken post in the Qara-Derrah Pass, a strong defile in the mountains which at a subsequent period formed the boundary between the Turkish and Persian dominions. With equal promptitude and decision the young prince resolved on an attempt to cut off this detachment and accordingly coming upon them with a suddenness which precluded resistance all those who could escape fled with the utmost consternation to the Bendimahi river which flows into the Lake Van.