It was one of the most impregnable large Islamic cities in the North-West of Afghanistan. The son of Genghis Khan moved towards it with his horrifying forces, and it was not saved from the same destiny of both Marw and Nishapur.

All its men were killed and all its women captured, and the entire city ruined and burnt, even though its governor, Maalik Khaan, was able to escape, along with a brigade of his army, towards Ghaznah, South of Afghanistan. That was the state of the kings and rulers of that time; they were successful in flight, leaving their peoples to fall prey in the talons of the Tatars.

By the fall of Herat, the entireterritory of Khuraasaan fell in the hands of the Tatars. They left no city in it without destruction. All of those incidents took place only in one year, i.e. the year 617 A.H., thereby recording one of the most terrifying events the earth has ever witnessed.

https://en.islamstory.com/index.php/en/artical/20720/invasion-herat