Unfortunately for him, Hasan had been imprisoned by Arghun Shah, the chief of the neighboring Jauni Kurban tribe and a partisan of Togha Temur.
Arghun Shah, however, had sent most of his forces to support Togha Temur's campaign against the Chobanids, giving Mas'ud the opportunity to cross through the territory of the Jauni Kurban and free Hasan.
Mas'ud apparently believed that, as long as he maintained his status as Togha Temur's vassal by sending tribute and keeping the khan's name on the coinage, that the latter would be willing to ignore this attack against Arghun Shah.
The remnants of the army, which fled in the direction of Mazandaran, was pursued by the Sarbadars, who killed many of Togha Temur's officials.
Furthermore, although Sabzewar was largely Shi'i, the recently conquered territories had a majority Sunni population, making Hasan's influence there minimal.
Although a conflict between Mas'ud and Hasan seemed inevitable, they both agreed to lead a campaign against the Kartids of Herat, who were nominally vassals of Togha Temur.
The Sarbadars marched on Herat in 1342; they were met by the Kartid malik Mu'izzu'd-Din Husain at Zava and the two sides began to fight.
The battle at first seemed to go well for the Sarbadars, but then Hasan Juri was struck down by an assassin, and his followers, suspecting Mas'ud,[3] immediately abandoned the battlefield.
Mas'ud had successfully regained sole control of the Sarbadars, although he had permanently alienated Hasan's dervish organization in the process.
The khan was still restricted to Mazandaran, so Mas'ud began seeking the support of the local rulers against Togha Temur.