During the reign of Sultan Sanjar or Sinjar of the same house, in the middle of the 11th century, Mer y was overrun by the Turkish tribes of the Ghuzz from beyond the Oxus.
Its most conspicuous feature is the burial mosque of Sultan Sanjar, reputedly dating from the 12th century.
Under the Tahirids of Khorasan, the Saffarids of Seistan and the Samanids of Bokhara, it flourished for some centuries in peace and progressive prosperity; but during the succeeding rule of the Ghaznevid kings its metropolitan character was for a time obscured by the celebrity of the neighbouring capital of Ghazni, until finally in the reign of Sultan Sanjar of Mer y about 1157 the city was entirely destroyed by an irruption of the Ghuzz, the predecessors, in race as well as in habitat, of the modern Turkomans.
In 1141 the assistance of this Khitaian prince was invoked by the shah of Kharezm against Sanjar, the Seljuk sovereign of Persia, who had expelled the shah from his kingdom and killed his son.
The Gur Khan came with a vast army of Turks, Khitaians, and others, and defeated Sanjar near Samarkand (Sept.
In this event - the defeat of Sanjar, whose brother's son, Mas'ud, reigned over western Persia - occurring four years before the story of the Eastern conqueror was told at Rome to Bishop Otto, we seem to have the destruction of the Samiardi fratres or Sanjar brothers, which was the germ of the story of Prester John.