Through the cunning of their ambitious prefect, Sejanus, the Guard was brought from their Italian barracks into Rome itself. In AD 23, Sejanus convinced Tiberius to have the Praetorian fort built just outside Rome. One of the cohorts held the daily guard at the imperial palace. Henceforth the entire Guard was at the disposal of the emperors, but the rulers were now equally at the mercy of the Praetorians. The reality of this was seen in AD 31 when Tiberius was forced to rely upon his own "cohors praetoria" against partisans of Sejanus. Although the Praetorian Guard proved faithful to the aging Tiberius, their potential political power had been made clear.