Juwaini writes that 13,00,000 people were killed in Merv by Genghis Khan. According to him, it took 13 days to count the dead. Almost 1,00,000 corpses were counted each day.
Several historians believe that such impossible numbers are nothing more than exaggerated accounts of Persian chroniclers. The main reason for such an expression could be the terror created by Genghis Khan during his ruthless campaigns. Genghis Khan annihilated and massacred without mercy. The Persian terrified and filled with anger for Genghis Khan portrayed him as a ruthless conqueror and stated exaggerated accounts of his killings.