The beginning of 7th/13th century was a terrible age for the whole Islamic rulers of Central Asia when the Mongol hordes emerged from Mongolia and began to threaten the Islamic world. The Mongols were a people of the Siberian forest who came from north into the slippers of Mongolia. They lived in a wild and primitive state of society, and their invasion inflicted more suffering on the human race than any other incident recorded in history of mankind. The monstrous hosts indiscriminately annihilated populations, pillaged towns and cities, wreaked special vengeance upon those who dared to resist them, and to whom they had promised immunity, converted the rich and smiling fields into deserts, and left behind the smoke of burning towns. Ruthlessly exterminating young and old, male and female, they obliterated cities and towns with their denizens, their schools, their mosques, their palaces, their libraries, their art treasures, largely nomadizing the region.
The Mongol empire, carved out at the expense of the Chi'n dynasty in North China, and the Sung in South China, was founded by Temujin (1162-1227), who assumed the name of Chenghiz Khan. He united the Mongol tribes and was acclaimed paramount Khan of the Mongols by an assembly (quariltai) of Mongol chiefs in 602/1206 at Karakorum. Beginning with campaings in 601/1205, 603/1207 and 605/1209, he led the Mongols to destroy the rules of western Asia. Late in 625/1219 he advanced towards the Jaxartes. In 626/1220, he crossed Jaxartes and marched straight on Bukhara, whose cultural heritage, the accumulated intellectual wealth of centuries were obliterated in plunder, bloodshed and arson.
It must be remembered that the Ozbek's war with Mengli ended in 14 to 15 months, but Jalaluddin Hasan prolonged his stay in Azerbaijan for 18 months. He was well kept with the terrible storms of the Mongols in Iran, therefore, he at once sent his envoys to Chenghiz Khan in Karakorum on 616/1219. The ambassadors of the Imam met Chenghiz Khan in the spring of 618/1221 at Balkh. He was the first among the Muslim rulers to send messages of good will to the Khan. His another precaution seems to reveal from his prolonged stay in Azerbaijan, where he had possibly selected a most suitable region to repair during emergency for himself or for his son, or grandson or any other. It seems that he had mapped out in this context an unscathed route from Alamut to Azerbaijan.
In 618/1221, Jalaluddin Hasan attended a banquet, where his enemies poisoned him. His vizir, who was the tutor of his successor, accused Imam's Sunni wives of Gilan in the conspiracy. It however resulted his death of dysentry in Ramdan, 618/November, 1221. His period of Imamate and rule lasted for 11 years, and was succeeded by his only son Alauddin Muhammad, who was then nine years old.