"An Historical Atlas of Central Asia" written by Yuri Bregel. This is stated on Page no 35 of this book.


By 1201 the Ghurid empire reached its greatest might, but it was followed by a rapid decline. When the Ghurids took over all of Khorasan after the death of Khorezmshah Tekesh, they caused the resentment in the local population by their financial levies and confiscations of grain, and the new Khorezmshah, #Ala ad-Din Muhammad, was able to restore his possessions there. In 1201 the Khorezmshah Muhammad besieged Herat, but had to retreat before the Ghurid army. Later the same year Muhammad captured Nishapur and in 1203, after the death of the Ghurid sultan Ghiyath ad-Din Muhammad, he conquered Merv. In 1204 he besieged Herat again, but was repulsed by the Ghurid sultan Shihab ad-Din Muhammad, who pursued the Khorezmian army into Khorezm itself. The Khorezmians opened the dikes on the canals and flooded the countryside; but after the water receded,
the Ghurid army defeated the Khorezmshah near his capital, Gurganj, and besieged the city.
The Khorezmshah turned for help to his Qara-Khitay suzerains, who came to his aid accompanied by the troops of their Qarakhanid vassals from Samarqand and Otrar. Shihab ad-Din was defeated, and the Qara-Khitays pursued him to Andkhud, where he was defeated again and besieged. A truce signed due to the efforts of Sultan #Uthman, the Qarakhanid ruler of Samarqand, allowed Shihab ad-Din to escape, but early in 1206 he was assassinated, and soon thereafter the Ghurids lost all of Khorasan, except Herat.