Tarikh-i Jahangushay-i Juvaini

Tārīkh-i Jahāngushāy (Persian: تاریخ جهانگشای‎‎ "The History of The World Conqueror") or Tārīkh-i Jahāngushāy-i Juwaynī (تاریخ جهانگشای جوینی) 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 Tajikistan 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.

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Wikipedia