The siege of Herat of 1381 was an easy success that ended Tamerlane's first major campaign in Khorasan and saw his empire expand out of its original base in Transoxiana into the former empire of the Il-Khans in Persian for the first time.
Tamerlane's earlier campaigns had been fought largely within the former Chaghatay Khanate, either against Moghulistan to the east, or Khwarezm, the area to the north-west of Transoxiana, and that had once been split between Chaghatay and the Golden Horde.
By the end of the 1370s Tamerlane began to look south and west into the former empire of the Il-Khans, the Mongol rulers of greater Persia. This empire had collapsed in the middle of the fourteenth century, and its lands were ruled by a large number of independent princes. Herat, at the eastern end of the empire in Khorasan, was ruled by the Kart dynasty, a family that had ruled the city as vassals of the Il-Khans since the mid thirteenth century. Earlier in his career Tamerlane had fought for Malik Muizz ad-din Husayn, the previous head of the dynasty, but now he saw himself as the restorer of the Mongol empire, and the current ruler of Herat, Ghiyas ad-Din Pir Ali, as his vassal.
In 1379 Tamerlane summoned Ghiyas ad-Din to one of his formal gatherings. Ghiyas ad-Din attempted to win extra time by pretending to accept the summons, but when Tamerlane's envoy reached Herat it was clear the city was being prepared for war.
In 1380 Tamerlane appointed his youngest son, the fourteen year old Miranshah, as governor of Khorasan, and a limited campaign was fought, before in 1381 Tamerlane himself took to the field. After some preliminary movements his army stormed the fortified city of Fushanj, thirty miles to the west of Herat, slaughtering the garrison and plundering the city.
From Fushanj Tamerlane advanced east against Herat, now defended by Ghiyas ad-Din in person. His army arrived outside the walled city, and promptly destroyed the gardens that ringed the city, before beginning to dig siege works towards the fortifications. Ghiyas ad-Din responded by leading some of his best men out of the city in a sally, but this was repulsed after some fierce fighting.
The fate of Fushanj and the failure of this sally undermined to morale of the inhabitants of Herat. Ghiyas ad-Din attempted to restore their morale by organising a second rally, but this failed to gain support. With his position within the city crumbling Ghiyas ad-Din submitted to Tamerlane, sending his wide and son to arrange the surrender.
The cost to Herat of this short siege was largely financial. Tamerlane's men looted the treasure accumulated by the Kart kings, while the inhabitants were forced to pay a large ransom. The city walls were demolished and two hundred of the wisest men of the city were ordered to men to Tamerlane's birthplace of Shakhrisabz. The King's Gate of Herat, an iron gate covered in sculpture and inscriptions, was also taken to Shakhirsabz.
Only two years late Herat was involved in a revolt against Tamerlane. This time he was less merciful, sending his son Miranshah to Herat to crush the rebellion. The surviving members of the Kart dynasty were executed, and piles of skulls built outside the city. After this Herat remained quiet.