 In response, Iyas commanded pro-Sassanid Arab and Persian troops against the Banu Bakr at the Battle of Dhi Qar in 609, in which the Sassanids were defeated.According to historian Irfan Shahid, evidence suggests clans of the Tayy moved into Byzantine-held Syria beginning in the 6th century.By then, the Ghassanids had largely supplanted the Salihids as the Byzantines' main foederati, and the Salihids began living alongside the Tayy in the region of Kufa.