Jelal ud din vanished then for a time from the conflict to appear later on in various struggles till weakness, treachery and death put an end to him. Mongol generals crossed the river and pursued, but returned after fruitless endeavors. Jinghis marched up the right bank of the Indus in the spring of 1222, and sent his son Ogotai to take Ghazni and destroy it. Here, as in most other places, the inhabitants were sent from the city, as it were to be counted, but were slaughtered most brutally; none were spared except artisans. An army corps was sent also to ruin Herat, the one city left in Khorassan. Herat had risen in revolt on hearing of the Peruan triumph over Mongols; the people had had such action in view since the time of surrender, and had stored away arms and supplies under pretext that they were for Mongol use should the need come. Not far from Herat was the Kaliun fortress, known later on as Nerretu. To reach this strong place men had to pass single file on the high, narrow ridge of a mountain which resembled the back of a colossal hog of the razor-back species. The place was beyond reach of arrows, or of stones sent by catapults. Though they had attacked Kaliun twice, the Mongols had failed in their efforts to take it. The Kaliun men, fearing lest they might come a third time, and impress Herat people, had planned to involve that strong and wealthy city, which would then have one cause with them. They sent letters to the Mongol governors ruling in Herat stating: “We are ready to surrender, but fear Mongol rigor; we beg for a written safe-conduct.” The governors answered that they would give such a letter, and advised the petitioners to visit the city and come to them. This was all that the other men needed; so seventy strong warriors went down from Kaliun, disguised as simple huxters; they had arms covered up in the packs which they carried. They entered the city, each man by himself, combined later on and slew both the governors. Herat rose immediately, and killed every partisan of the Mongols. In addition to his own men the Mongol commander led now fifty thousand impressed from conquered places. A siege followed soon and a desperate resistance. Six months and seventeen days did it last till the fall of the city. The sword was turned then on all save the choice youth of both sexes. For one week the Mongols slew, pillaged, burned, ruined. It was said that one million six hundred thousand people perished in the conflict and subsequent slaughter. Jinghis received the richest of the plunder, and with it went several thousands of youthful captives. When Herat was destroyed the commander went back to the main army; somewhat later troops were sent to capture all who might have escaped and appeared in the ruins; they found about two thousand. These they slew, and then returned to those who had sent them.