Tarikh - i Jahangushay - i Juvaini Tarikh - i Jahangushay - i Juvaini ( " The History of The World Conqueror " ) is a detailed historical account written by the Persian Ata - Malik Juvayni describing the Mongol , Hulegu Khan , and Ilkhanid conquest of Persia as well as the history of Isma ' ilis . It is also considered an invaluable work of Persian literature . This account of the Mongol invasions of his homeland Iran , written based on survivor accounts , is one of the main sources on the rapid sweep of Genghis Khan ' s armies through the nomadic tribes of Tajikstan and the established cities of the Silk Road including Otrar , Bukhara , and Samarkand in 1219 , and successive campaigns until Genghis Khan ' s death in 1227 and beyond . His writing is sometimes inflated , as when he estimates the strength of the Mongol army at 700 , 000 , against other accounts that put the number between 105 , 000 and 130 , 000 . His descriptions are often written from a sense of drama : of the fall of Assassin castle Maymun - Diz in November 1256 , where he was present at the siege , he describes the effect of trebuchet ( catapult ) bombardment on the battlements : The first stones which were discharged from them broke the defenders ' trebuchet and many were crushed under it . Fear of the quarrels from the crossbows overcame them so that they were in a complete panic and tried to make shields out of veils [ i . e . they did best to defend with very indadequate equipment . ] Some who were standing on towers crept in their terror like mice into holes or fled like lizards into the crannies of the rocks . Juvayni ' s descriptions are , however , a very valuable resource for contemporary Mongol history , along with the work of Rashid al - Din , and the Secret History of the Mongols . One of his convincing descriptions is that of the Mongol hunt or " nerge " as an army training exercise for the nomadic Mongols . In a nerge the whole army rounded up all the animals over a large region , in order to obtain dried meat before the onset of winter . In the time of Genghis Khan , the nerge was converted into an exercise in discipline with severe punishments ( the Yasa / Jasa / Zasagh is withoout respect of persons and according to the author Mirhond enjoins corporal punishment without respect of persons for those who allow animals to escape ) for commanders of tens , hundreds , or thousands , who let animals escape . Once rounded up , the animals were ruthlessly massacred , first by the Khan , then by princes , and finally , only after so commanded , by all the army . This was to form a model for the ruthlessness of Mongol attacks on well - established human settlements . The painting of Khubilai Khan and his Khatun Chabi who was childless however would show an average hunt with slow - moving horses and watching for quarry . The sadistical scene envisioned by Juvaini wherein crowded animals of all types seek to flee , seems too close to the promised biblical Day of Judgement , since lions would have attacked oxen . Nonetheless it is likely that Hulagu Khan and his Christian Khatun Doqez increased hunting due to their Latin allies , who also may have impeded Mongol victory at Ain Jalut . However a limited symbolic release of animals and capture of animals allegedly for breeding has been recorded , on http : / / mongolconquest . devhub . com / blog / 645606 - the - mongols - of - genghis - khan / , but the Jasa / Yasagh / Zasagh forbids hunting during the breeding season . A poignant account of the tragic failure of a Chinese student - ( Jiang Rong : " The Wolf " ) - to save a wild wolf of a type formerly hunted by the historical Mongol people and their descendants still today , would indicate wolves were targeted by such hunts as traditional methods of the ravaging wolves in imminent danger of extinction were described . Snow leopards and others were also likely to have been hunted . It is reported in " Mongol Warrior 1200 - 1350 " by Stephen Turnbull and Wayne Reynolds available on Google Books that the Mongols ate horse milk powder with water , around 250 grammes a day although an account they quote mentions they took 4 . 5 kg along for an expedition , and claims they hunted on campaign , such as digging around for marmots , it also said they ate horse meat ( it is known that the wild Przewalski horses were eaten which contributed to their extinction , but that may have been due to food shortage and was later than the period of the historical Mongols when possibly even these horses were some of them still domestic ) , on the other hand they also drank blood from their horses by temporarily opening a vein when in shortage . However it is also stated that they failed at times to prevent their horses from dying of hunger . However , William of Rubruck , reports a more moderate but identical style of hunting specifically of the Tatars , so Juvaini could still be exaggerating . After the fall of Merv in Turkmenistan , the people were rounded up and distributed among the soldiers in tens , hundreds and thousands , and each man in the remaining Mongol army was assigned the execution of " three to four hundred people . " However , there is no doubt that this type of savagery was part of the terror spread by the Mongol army .