Asia and Transoxiana experienced a truly golden age. Bukhara became one of the leading centers of learning, culture, and art in the Muslim world, its magnificence rivaling contemporaneous cultural centers such as Baghdad, Cairo, and Cordoba. Some of the greatest historians, scientists, and geographers in the history of Islamic culture were natives of the region including al-Bukhari, Al-Tirmidhi, al Khwarizmi, al-Biruni, Avicenna and Omar Khayyam. As the Abbasid Caliphate began to weaken and local Islamic Iranian states emerged as the rulers of Iran and Central Asia, the Persian language continued its preeminent role in the region as the language of literature and government. The rulers of the eastern section of Iran and of Transoxiana were Persians. Under the Samanids and the Buyids, the rich Perso-Islamic culture of Transoxiana continued to flourish. Ghaznavids, Karakhanids and Anushteginids In the sixth century, the continued influx of Turkic nomads from the northern steppes brought a new group of people into Central Asia. These people were the Turks who lived in the great grasslands stretching from Mongolia to the Caspian Sea. Later, introduced mainly as slave soldiers to the Samanid Dynasty, these Turks served in the armies of all the states of the region, including the Abbasid army. In the late tenth century, as the Samanids began to lose control of Transoxiana (Mawarannahr) and northeastern Iran, some of these soldiers came to positions of power in the government of the region, and eventually established their own states, albeit highly Persianized. With the emergence of a Turkic ruling group in the region, other Turkic tribes began to migrate to Transoxiana. The first of the Turkic states in the region was the Persianate Ghaznavid Empire, established in the last years of the tenth century. The Ghaznavid state, which captured the Samanid domains south of the Amu Darya, was able to conquer large areas of eastern Iran, Central Asia, Afghanistan, and Pakistan during the reign of Sultan Mahmud. The Ghaznavids were closely followed by the Turkic Qarakhanids, who took the Samanid capital Bukhara in 999 AD, and ruled Transoxiana for the next two centuries. Samarkand was made the capital of the Western Qarakhanid state. The dominance of Ghazna was curtailed, however, when the Seljuks led themselves into the western part of the region, conquering the Ghaznavid territory of Khorazm (also spelled Khorezm and Khwarazm). The Seljuks also defeated the Karakhanids, but did not annex their territories outright. Instead,