Lucullus' reaction was an attack that was so precipitate that he took Tigranes by surprise. According to Roman historians Mithrobazanes, one of Tigranes' generals, told Tigranes of the Roman approach. Tigranes was, according to Keaveney, so impressed by Mithrobazanes' courage that he appointed Mithrobazanes to command an army against Lucullus – Tigranes sent Mithrobarzanes with 2,000-3,000 cavalry to expel the invader. Mithrobarzanes charged the Romans while they were setting up their camp, but was met by a 3,500-strong sentry force and his horsemen were routed. He perished in the attempt. After this defeat, Tigranes withdrew north to Armenia to regroup, leaving Lucullus free to besiege Tigranocerta.