The Praetorian Guard was the elite bodyguard of the Roman emperor that existed from the start of the Roman Empire in 27 BC until Constantine the Great dissolved the guard in 312 AD after the Battle of Milvian Bridge. The Praetorians were not just bodyguards, but also elite soldiers; praetorian cohorts fought on the field many times. They were also significant due to their role in politics; ten Roman emperors were killed by the Praetorian Guard (Caligula, Galba, Pertinax, Didius Julianus, Elagabalus, Maximinus Thrax, Pupienus, Balbinus, Gordian III, and Aurelian), which often nominated its own prefect - or any sympathetic politicians - as the new emperor. For this reason, they clashed with the Roman Senate, as seen in the murders of Pupienus and Balbinus by the Praetorians due to their appointment by the Senate. The Praetorians were headquartered at the Castra Praetoria in Rome, putting them near the emperors. Constantine the Great dissolved the Praetorian Guard in 312, ending the long-lasting Praetorian legacy.