What was the role of army …

Next to the emperor and the Senate, the other key institution of imperial rule was the army. Romans had a paid professional army where soldiers had to put in a minimum of 25 years of service. The army was the largest single organised body in the empire with 600,000 soldiers in the fourth century. The soldiers would constantly agitate for better wages and service conditions. These agitation often took the form of mutinies.

The emperor, the aristocracy and the army were the three main ‘players’in the political history of the empire. The success of individual emperors depended on their control of the army, and when the armies were divided, the result usually was civil war. Except for one notorious year (69 CE), when four emperors mounted the throne in quick succession, the first two centuries were free from civil war.