Rokn ud din informed Hulagu of this trouble, and the peril in which he then found himself. In answer Hulagu begged him not to expose his life needlessly. Meanwhile the catapults were mounted and the following morning an attack was begun from all points. The combat lasted till evening and was strenuous on both sides. At a season when tempests and snow had till that year made all mountain places impassable the weather was favorable for siege work and a new attack. The fourth day was opening when Rokn ud din thought it best to abandon the fortress. He sent his chief men with his son to the camp of the Mongols, and went himself the next morning to fall prostrate in presence of Hulagu. With him went his minister, the famous astronomer, Nassir ud din, and two great physicians, who had always advised a surrender. Next day the Mongols marched into Meimundiz. Hulagu treated Rokn ud din kindly, but Mongol officers watched him and he was forced to direct Ismailian commandants to surrender their fortresses. He himself had to go with Hulagu’s agents to effect every transfer. More than forty strong castles surrendered; all were destroyed when their garrisons had withdrawn. Alamut and Lemsher were the last strongholds left standing and their commandants declared that they would yield only when Hulagu came in person, and Rokn ud din ordered the transfer. Hulagu set out for Alamut and halted nine days at Sheherek, the ancient residence of the Dilem rulers, where he celebrated the happy end of his enterprise. After that he appeared before Alamut and sent Rokn ud din to summon his people to surrender. The commandant refused. Hulagu sent now a large corps of men to lay siege to the fortress. At this the garrison offered to yield, and sent deputations repeatedly to Rokn ud din to intercede in their favor, and save them. Three days were given to remove what belonged to the garrison personally. On the fourth day the Mongols and Persians marched in, seized what was left and set fire to the buildings. Hulagu, it is said, himself visited the fortress and was amazed at the height of the mountains around it. The library of Alamut was renowned in those regions, but the vizir and historian, Ata ul Melik Juveini, who asked and obtained Hulagu’s permission destroyed every manuscript which related to Ismailian opinions and teaching.