Seljuk gave his name to both the empire and the Seljuk dynasty. The Seljuks united the fractured political landscape of the eastern Islamic world and played a key role in the first and second crusades. Highly Persianized in culture and language, the Seljuks also played an important role in the development of the Turko-Persian tradition, even exporting Persian culture to Anatolia. The settlement of Turkic tribes in the northwestern peripheral parts of the empire, for the strategic military purpose of fending off invasions from neighboring states, led to the progressive Turkicization of those areas.