An Historical Atlas of Central Asia" written by Yuri Bregel. This is stated on Page no 29 of this book.


After the Seljuk victory at Dandanaqan in 1040 (see map 13), the Seljuks continued their conquests in Iran. According to the division of authority made by the Seljuks after their victory, Toghril, the supreme sultan, was in charge of the lands conquered in the west, while Khorasan and the east remained under Chaghri Bek.
But first their attention was diverted to the north. The Oghuz in the lower course of the Sir-Darya experienced an
increasing pressure from the Qipchaqs and other nomadic groups as a result of the large scale east-west migrations in the steppes that took place in the first half of the 11th century (see map 13); a part of the Oghuz began to migrate across the Volga into the East European steppe, while many others migrated to Khorasan and joined the Seljuks.
Those under the Oghuz yabghu Shah Malik attacked the Khorezmshah Ismail Khandan in 1041, defeated him in a three-day battle, and conquered Khorezm. Ismail fled to Khorasan, and in 1043 the combined forces of Toghrïl and Chaghrï drove Shah Malik from Khorezm; he fled to Dithietane and from there to Mekran (in southern Iran) where he was captured and later executed.
Khorezm was placed under a Seljuk governor; in the 1050s the governor rebelled and was subdued by Chaghrï Bek, who at that time also received the submission of the “Amir of the Qïpchaqs” (apparently, on the Sïr-Darya). Toghrïl returned from Khorezm to Iran; in 1043 he entered Rayy, and in 1050 he conquered Isfahan, which became his capital. The continuing pressure of the Qïpchaqs on the remaining Oghuz in the lower Sïr-Darya region caused the migration of most of them to Khorasan, Azerbaijan and Iraq, where they joined the Turkmens who came there in the 1030s; but some of them probably went to the Mangïshlaq peninsula, where Sultan Alp-Arslan had to fight them three decades later.
The Turkmens under Toghrïl and other members of the Seljuk family (but also often on their own) overran all of Iran, Iraq, and Azerbaijan. In 1055 Tughrik entered Baghdad; he married the daughter of the #Abbasid caliph, and the latter bestowed on him the honorific title Malik al-Mashriq wall-Maghrib (“King of the East and West”).
The dynasty founded by Tughrik Bek became known in the historical literature as the “Great Seljuks” (as distinct from various local dynasties founded later by the members of the same clan). The Shiite Builds were eliminated, and the Seljuks vigorously promoted Sunni Islam in their possessions.
In the east, after indecisive warfare with the Ghaznavids, a peace agreement was signed in 1059 between Chagrin Bek and Ibrahim b. Masoud, establishing the borders between the two empires; the peace was generally maintained to the end of the century.