The Roman Army, 31 BC–AD 337: A Sourcebook

182 The Roman Army
The Roman emperor held his powers by virtue of a law on the
vote of the people, though in practice a decree of the senate determined
this. But that was a formality and the senate had no right to choose
and make emperors. Nor had the army, which, along with the senate
and people, was the other permanent institution in the Roman state.
For the law made no mention of the emperor’s command of the army.
Moreover, although the troops might be loyal to a dynasty there was
no rule of dynastic succession, since at the start Augustus at least in
public was not establishing a monarchy. An emperor emerged,
therefore, through a number of factors—connection to the previous
emperor by birth or adoption, the goodwill of senate and people, a
demonstration of support by the praetorians under the direction of
the influential praetorian prefects, and the acquiescence of governors
and soldiers in the provinces. So, in certain circumstances the support
of the praetorians or the legions could be decisive, and in a sense
soldiers could informally ‘make’ an emperor. The events of AD 68/69
openly demonstrated the potential importance of provincial army
commanders, but the practices and ambiguities of the Augustan
principate worked well, and in the next 125 years there were only
two attempts (by Saturninus in AD 89 and Avidius Cassius in AD
175) to follow this example.
After the violent usurpation of power by Septimius Severus in AD
193, in a period of just over forty years, four emperors in succession
met violent deaths, three of them as a result of military rebellion. The
balance between the various roles that an emperor had to play had
shifted. The army’s position in political life was increasingly important
and also more visible; the soldiers now looked for greater financial
rewards and were more insistent in opposition if they did not get
what they wanted. The emperor, who had all the trappings of a
commander-in-chief, was under increasing pressure to spend more
time with his troops, and to show himself a good comrade and
competent military leader, and indeed to assume the attitudes and
demeanour of a war lord. Capacity to rule was dangerously associated
with ability to control and direct an army. Maximinus, who overthrew
Severus Alexander, became the first Roman emperor personally to
fight in battle (Campbell 1984:365–414; the emperor as commanderin-chief—chapter
3).
The following extracts, set out in chronological order by the period
to which they refer, are intended to illustrate some of the ways in which
ancient writers thought in general terms about the army and its
developing role in politics, its part in the making and removing of
emperors, and the dangers of civil war.