THE ROMAN EMPIRE in At first these armies consisted of the regular Roman legions composed of Roman citizens, and of an approximately equal number of local levies. It will be convenient m ^ ... , , , • The Armies, to remember that in numbers the legion corre- sponded roughly to what we call a brigade, divided into cohorts which were the equivalent of regiments. But whereas with us a brigade is a group of regiments, with the Romans the cohort was a division of the legion. The legion was the unit, whereas with us the regiment is the unit. Of very great importance also was the institution of a privileged body of troops called the Praetorian Guard, under an officer called the prefect, who held his appoint- The Prae ment from the princeps. This was theoretically torian the force behind the government for the control Guard - of the capital. But it was the one powerful military body at the headquarters of government; and it was not long before it found itself able to exercise a decisive control, whenever it was disposed to intervene, on the succession to the Principate. This then was the organisation which made the princeps absolute master of the whole Roman state. Its weakest point lay in what was at the outset the necessity of pretending that Augustus had saved and restored the republic, which Anthony had threatened to transform into an oriental despotism. The despotism of Augustus had to pass itself off as nothing more than a temporary authority conferred on an individual to deal with a prolonged emergency. In the nature of things Augustus was barred from making open provision for the The Succes . establishment of a dynasty ; and matters were sion to the made worse by the failure of heirs of his body, and cipate. the difficulty of arriving at any principle for establishing the course of succession. At his death the problem was solved for the time by the fact that his kinsman Tiberius was associated with him in the possession of the tribunician and proconsular powers, so that if any attempt had been made to resist his succession he could have secured it by force. Theoretically, the succession went by the election of the Senate ; practically, if the Praetorian Guard had a mind to override the election of
