Ubaydallah ibn Abdallah ibn Tahir was the last major Tahirid to hold high office in what dynasty?
Tahirid dynasty The Tahirid dynasty (Persian: طاهریان‎ ‎ , "Tâhereyân") was a dynasty, of Persian dihqan origin, that governed the Abbasid province of Khorasan from 821 to 873 and the city of Baghdad from 820 until 891. The dynasty was founded by Tahir ibn Husayn, a leading general in the service of the Abbasid caliph al-Ma'mun. Their capital in Khorasan was initially located at Merv but was later moved to Nishapur. The Tahirids enjoyed a high degree of autonomy in their governance of Khorasan, but they remained subject to the Abbasid caliphate and were not independent rulers.
Abdallah ibn Amir Abdallah ibn Amir (Arabic: عبدالله بن عامر‎ ‎ ) was a governor of Busra (647–656) and an extremely successful military general during the reign of Rashidun Caliph Uthman ibn Affan. His father was a maternal uncle of Caliph Uthman. Abdallah was thus a cousin of Uthman. He is well known for his administrative and military prowess. his campaign of Reconquest and pacifying the large soils of Persian Empire former territories has left great legacy of Islamization in both Iran and Afghan land