Excerpts from Books and Wikipedia
"The Seljuqs, who like the Ghaznavids were Persianate in nature and of Turkic origin, slowly conquered Iran over the course of the 11th century. . . . They established a Sunni Muslim rule over parts of Central Asia and the Middle East from the 11th to 14th centuries. . . . Today they are regarded as the cultural ancestors of the Western Turks, the present-day inhabitants of Azerbaijan, Turkey, and Turkmenistan, and they are remembered as great patrons of Persian culture, art, literature, and language. The dynastic founder, Tughril Beg, turned his army against the Ghaznavids in Khorasan. He moved south and then west, conquering but not wasting the cities in his path. In 1055 the caliph in Baghdad gave Tughril Beg robes, gifts, and the title King of the East. Under Tughril Beg's successor, Malik Shah (1072–1092), Iran enjoyed a cultural and scientific renaissance, largely attributed to his brilliant Iranian vizier, Nizam al Mulk. These leaders established the observatory where Omar Khayyám did much of his experimentation for a new calendar, and they built religious schools in all the major towns." [Wikipedia] "[The Great Seljuk Empire] would be a major force during the first two Crusades and an antagonist to the Byzantine Empire over the next century." [Wikipedia: Timeline of Middle Ages]