The Samanid Empire, 819 to 999, restored Persian control of the region and enlarged the cities of Samarkand and Bukhara (both cities are today part of Uzbekistan) which became the cultural centers of Iran and the region was known as Khorasan. The empire was centered in Khorasan and Transoxiana; at its greatest extent encompassing modern-day Afghanistan, large parts of Iran, Tajikistan, Turkmenistan, Uzbekistan, Kyrgyzstan, parts of Kazakhstan, and Pakistan. Four brothers Nuh, Ahmad, Yahya, and Ilyas founded the Samanid state. Each of them ruled territory under Abbasid suzerainty. In 892, Ismail Samani (892–907) united the Samanid state under one ruler, thus effectively putting an end to the feudal system used by the Samanids. It was also under him that the Samanids became independent of Abbasid authority. The Kara-Khanid Khanate conquered Transoxania (which corresponds approximately with modern-day Uzbekistan, Tajikistan, southern Kyrgyzstan, and southwest Kazakhstan) and ruled between 999 and 1211. Their arrival in Transoxania signalled a definitive shift from Iranian to Turkic predominance in Central Asia, but gradually the Kara-khanids became assimilated into the Perso-Arab Muslim culture of the region.