The article focuses on the genesis of the praetorian cohorts and their transformation into the imperial guard. Praetorian guard, founded by Octavian Augustus, according to some researchers, led its origin from the Praetorian cohorts during the Civil War. According to the author, the civil wars of the 1st century BC, cannot be considered to be the main reason for emerging of the Praetorian guard, which contradicts the opinion expressed by a number of representatives of domestic and foreign historiography. The process of the birth of the imperial guard is closely related to Roman history. The impact of the Etruscans and the power of the first kings contributed to the emergence of such an institution as the lictors. In the future, the aggressive foreign policy of Rome (in Latium, the Apennines and the Mediterranean) led to the formation of special security units commanders, such as ablekts, extraordinaries and praetorian cohorts. The struggle between the various factions in Rome in 1st century BC. strengthened the role of the military units in the political life of the state. The decisive factor for this was the civil war and the establishment of the principality regime. At the same time, in connection with the war in the East, the Institute of bodyguard experienced Hellenistic and Oriental influence.