Marwan prepared a massive strike for 737, intended to end the war for good. Marwan apparently went to Damascus in person to persuade Hisham to back this project and was successful: the 10th-century historian Bal'ami claims that his army numbered 150,000 men, comprising regular forces of Syria and the Jazira, as well as volunteers for the "jihad", Armenian troops under Ashot Bagratuni, and even armed camp followers and servants. Whatever the real size of Marwan's army, it was a huge force and certainly the largest ever sent against the Khazars. Marwan first secured his rear by subduing the Armenian factions who were hostile to the Arabs and their client Ashot. He then pushed into Caucasian Iberia, driving its Chosroid ruler to seek refuge in the fortress of Anakopia on the Black Sea coast, in the Byzantine protectorate of Abkhazia. Marwan laid siege to Anakopia itself, but he was forced to retire due to the outbreak of dysentery among his troops.