Excerpts from Books and Wikipedia
"The enemy was Togrul, the Turkish chief who had led his coalition in the conquest of the Ghaznavid lands west of the Indus mountains. Togrul had now been at the head of his tribe, the Seljuq Turks, for twenty years. They were, in the words of historian Rene Grousset, 'a horde without tradition, and the least civilized of all the nomad clans,' but Togrul had provided them with a path into nationhood. He had himself crowned sultan of the Turks in 1038 and had established his capital at Nishapur. His Turks were now strong enough to challenge Byzantium. . . . Constantine Monomachos decided to make a treaty with the Seljuq Turks instead of continuing to fight. In exchange for peace and the return of the captives, he agreed to give up some of the land on the eastern frontier. He also sent expensive gifts to Togrul and promised that he would allow Muslims to worship freely in Constantinople; the Turks had converted to Islam, and this was a gesture of friendship. Togrul accepted the terms and sent Constantine's commander back to Constantinople unharmed." [Bauer; Medieval World, p. 628-9]