The Seljuks were a tribe of Tartars who assumed power after the defeat of the grandson of Sultan Mahmoud of Ghizni, the patron of Firdousi. Their leader, Toghrul, established himself at Nishapur and extended his conquests to include Iraq. His nephew Alp-Arselan succeeded to the throne in 1063 and further consolidated the empire through the defeat of the Romans and Transoxonia. He was assassinated outside Berzem in 1072 and his son Malek Shah (1072-1092) was designated to succeed him, although the powers of state were entrusted to the vizier, Nizam-ul-Mulk.
Architecturally the Seljuk period is notable for the development in the use of brickwork which enabled buildings to be decorated with relief work which took full advantage of the strong sunlight in Iran to create an elaborate interplay of light and shade as epitomised by this brickwork on the shaft of the Minaret of Chehel-Dokhtaran. Much of the interior of Masjed-e-Jomeh also dates from this period.
Malek Shah's generals further extended the boundaries to the borders of China and a period of prosperity ensued under the guidance of Nizam-ul-Mulk. At the age of ninety the latter was discredited at the orders of the principal sultana, Toorkan Khatoon, who feared he would oppose her son's accession to the throne, and killed by a follower of Hassan Sabah, the leader of the mountain tribe of Assassins. Shortly after this Malek Shah died.
A period of civil war followed during which his brother and four sons disputed the empire which was eventually taken over by the third son, Sanjar. He suffered a series of reverses, being held prisoner by Turkomans between 1153 and 1156 during which time the empire was ruled from Khorassan by his favourite sultana. He escaped and died a broken man at the age of 73.
Some 40 years of civil war followed after which Toghrul III, who had united the empire once again, was defeated in battle in 1193 by the ruler of Khaurizm in Tartary, whose son in turn fell victim to Ghenghiz Khan and died in 1220.