Sulayman acceded upon al-Walid's death in 715 and appointed Yazid governor of Iraq, in place of the interim governor, the al-Hajjaj loyalist
Yazid ibn Abi Muslim. He initially took up office in Wasit, and "speedily aroused opposition ... because of his exactions and arbitrary rule", according to the historian
C. E. Bosworth. Yazid was wary of inviting the Iraqis' ire by emulating the stringent taxation policy of al-Hajjaj but also of falling short in revenue if he relaxed collections. Upon his request, the caliph divested him of fiscal authority and appointed
Salih ibn Abd al-Rahman, a career tax official, to head the provincial treasury, leaving Yazid to head military and religious affairs. Salih answered directly to Sulayman and had his own Syrian guard. He consistently declined Yazid's exorbitant requests of the treasury. Seeking to avoid Salih's financial constraints, Yazid persuaded the caliph to relocate to Khurasan in mid-716. While freeing himself of Salih's oversight was the motive ascribed to Yazid by the traditional sources, modern scholars consider the potential for greater profits in Khurasan and stronger tribal support there as additional motives. At the time, Khurasan had effectively been governed by the
Tamim tribal chief
Waki ibn Abi Sud for nine months. He had been chosen by the troops of Khurasan to lead them after their mutiny against Qutayba, who was killed attempting to revolt against Sulayman shortly after his accession. To justify replacing him, Yazid persuaded Sulayman that Waki was a rough
Bedouin lacking in administrative ability. In addition to Khurasan, Yazid retained the governorship of Iraq and thus became the practical viceroy of the East. In the words of the historian Muhammad Abdulhayy Shaban, he became "Sulayman's own al-Hajjaj". Bosworth comments that in Khurasan, distant from the caliphal center of power and with the solid backing of the Azdi soldiers, Yazid "could discriminate against the Tamim and other North Arab tribes and could engage in financial malpractices". The troops of Khurasan were largely drawn from the Basra garrison and were made up mainly of five tribal groups increasingly split into two factions: the Tamim and Qays of the 'northern' Mudar faction and the rival
Bakr and
Abd al-Qays, both grouped under the
Rabi'a, and the 'southern' (Yamani) Azd. According to the historian
Gerald Hawting, Yazid's period in office is associated with "the emergence of Mudari and Yemeni factionalism in the east", i.e. in Iraq and Khurasan. Yazid dismissed all of al-Hajjaj's appointees. Yazid persecuted the relatives and subordinates of Qutayba in Khurasan. In Iraq, he had directed Salih to oversee the arrest and torture of al-Hajjaj's relatives, including the conqueror of
Sind,
Muhammad ibn al-Qasim, who was killed; the torture was administered by Yazid's brother Abd al-Malik. He installed his loyalists throughout the East: out of the seventeen appointments made by him, fourteen were to Yamanis and one to the Yamani-allied Rabi'a. His deference to and promotion of the Azd may have stemmed from his and the Muhallabids' desire to secure themselves as leaders of the tribe in spite of their "fairly obscure origin", according to Hawting. Yazid's time in office represented the peak of Muhallabid power. He appointed his brothers Habib, Marwan, Mudrik and Ziyad as the respective subgovernors of Sind, Basra, Sijistan, and Oman, while his son Mukhallad governed Khurasan in Yazid's absence.
Campaigns in Jurjan and Tabaristan coast in the 8th century, including
Tabaristan,
Jurjan,
Gilan and
Daylam Qutayba had won renown for leading the troops of Khurasan to great conquests in Transoxiana, the massive region beyond the
Oxus River. According to the historian
Hugh N. Kennedy, "there is no doubt that Yazīd wanted to emulate him and show that he could lead armies against the
unbelievers and reward them with abundant booty". In early 716, Yazid attempted to conquer the principalities of
Jurjan and
Tabaristan, located along the southern coast of the
Caspian Sea. Ruled by local Iranian dynasties and shielded by the
Alborz Mountains, these regions had remained largely independent of Muslim rule, despite repeated attempts to subdue them. The campaign lasted for four months and involved a 100,000-strong army assembled from the garrisons of Kufa, Basra,
Rayy,
Merv and Syria. It marked the first deployment of Syrian troops, the elite military faction of the Caliphate, to Khurasan. The first target of the campaign were the isolated settlements of
Dihistan, north of the river
Atrek. There, Yazid blockaded the region's defenders, consisting mainly of Chöl Turks. According to one version of events, the sued for peace, obtaining amnesty from Yazid for him, his family and livestock. Yazid entered his territory, taking thousands of captives, including some 14,000 Turks whom he executed. In another version, the leader of Dihistan had retired to a small fortified island in the Caspian and made terms with Yazid, involving significant tribute, after a six-month siege. Once the Turks were defeated, Yazid proceeded to subdue Jurjan, which fell with little resistance, partly because some of the Iranian population were receptive to Arab protection from the Turks. He secured control of Jurjan by founding a city there (modern
Gonbad-e Kavus). Next, Yazid moved on Tabaristan, whose defenders had historically driven back attempts by Arab Muslim armies to enter the narrow passes of the mountains protecting their homeland. There, Yazid's initial success was reversed by Tabaristan's ruler,
Farrukhan the Great, and his coalition from neighboring
Daylam and
Gilan, both Caspian-adjacent regions northwest of Tabaristan, in later confrontations that year. After having beaten the defenders in the plains, Yazid's troops came under assault by the defenders as they ascended the mountains. While they did not inflict heavy casualties on the Arabs, many of the latter died falling into ravines during the chaotic retreat. Spurred on by Farrukhan's victory, the people of Jurjan revolted against the small Arab garrison left there and Yazid's army came close to becoming surrounded and annihilated. In Kennedy's words, "Only some clever diplomacy allowed him [Yazid] to make a peace deal, which could be portrayed as a success". In return for a tributary arrangement with Farrukhan, Yazid withdrew Muslim troops from the region. Tabaristan remained independent of Arab rule until 760, when it was conquered by the
Abbasids, the successors of the Umayyads, but remained a restive province dominated by local dynasts.
Second dismissal and imprisonment In a letter, Yazid congratulated Sulayman on the conquests of Tabaristan and Jurjan, which had eluded previous caliphs until "God made this conquest on behalf" of Sulayman. He reported substantial spoils from the campaigns, declaring the customary fifth of the booty owed to the caliph to be six million
dirhams. This huge sum was a boastful exaggeration. Since Yazid's campaign in Tabaristan was abortive, most of the booty must have come from Jurjan, according to the historian
Khalid Yahya Blankinship. The letter did not reach the caliph, who died in September 717, and was instead received by Sulayman's successor,
Umar II (). When Yazid did not forward to the caliph his fifth of the spoils from the Caspian campaigns, Umar recalled him from Khurasan and imprisoned him in
Aleppo for allegedly pilfering these spoils. The viceroyalty of the East was broken up, with
al-Jarrah ibn Abdallah al-Hakami appointed over Khurasan,
Adi ibn Artat al-Fazari over Basra and a member of Caliph Umar's family over Kufa named
Abd al-Hamid ibn Abd al-Rahman ibn Zayd ibn al-Khattab. ==Rebellion against the Umayyads==