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 Mawarannahr were Persians. Under the Samanids and the Buyids, the rich Perso-Islamic culture of Mawarannahr continued to flourish. Samanid Empire, Ghaznavids, and Kara-Khanid Khanate The Samanids were a Persian state that reigned for 180 years, encompassing a vast territoriy stretching from Central Asia to West Asia. The Samanids were descendants of Bahram Chobin, and thus descended from the House of Mihrān, one of the Seven Great Houses of Iran. In governing their territory, the Samanids modeled their state organization after the Abbasids, mirroring the caliph's court and organization. They were rewarded for supporting the Abbasids in Transoxania and Khorasan, and with their established capitals located in Bukhara, Balkh, Samarkand, and Herat, they carved their kingdom after defeating the Saffarids. The Samanid Empire was the first native Persian dynasty to arise after the Muslim Arab conquest. The four grandsons of the dynasty's founder, Saman Khuda, had been rewarded with provinces for their faithful service to the Abbasid caliph al-Mamun: Nuh obtained Samarkand; Ahmad, Fergana; Yahya, Shash; and Elyas, Herat. Ahmad's son Nasr became governor of Transoxania in 875, but it was his brother and successor, Ismail Samani who overthrew the Saffarids and the Zaydites of Tabaristan, thus establishing a semiautonomous rule over Transoxania and Khorasan, with Bukhara as his capital. Samanid rule in Bukhara was not formally recognized by the caliph until the early 10th century when the Saffarid ruler 'Amr-i Laith had asked the caliph for the investiture of Transoxiana. The caliph, Al-Mu'tadid however sent the Samanid amir, Ismail Samani, a letter urging him to fight Amr-i Laith and the Saffarids whom the caliph considered usurpers. According to the letter, the caliph stated that he prayed for Ismail who the caliph considered as the rightful ruler of Khorasan. The letter had a profound effect on Ismail, as he was determined to oppose the Saffarids. Since the 9th century, the Turkization of the population of the Central Asian interfluve has been increasing. At this time, a military system was created, in which the influence of the Turkic military was strong. In the 9th century, the continued influx of 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