6 THE ROMAN EMPIRE
unproblematic – he was quickly acclaimed by the senate – but he still found
it advisable to bribe the guardsmen, doubling Tiberius’ benefaction in
anticipation of their support (rather than, as in the case of Tiberius, as a
reward for services rendered). In the event, disenchanted guard offi cers saw
to Gaius’ murder. The guard’s loyalty was to the domus Caesaris rather than
to any individual member, even if he was the emperor. This was dramatically
confi rmed when Claudius was found hiding in the palace, taken to the
praetorian camp, and hailed as emperor. Claudius gave them a massive
donation. Senators who were at the time advancing their own candidacies
or debating a return to the Republic were left high and dry. Nero’s succession,
as Claudius’ adopted son, was also an easy one, his acceptance by the senate
never in doubt. But his fi rst port of call was the praetorian camp, to which
he was escorted by the praetorian prefect Burrus.^6 It was the declaration of
the praetorians for Galba that precipitated Nero’s suicide and inaugurated
the year of the four emperors (68–69). The praetorians soon betrayed Galba
for Otho. Vitellius knew what he was doing when he followed up Otho’s
defeat and suicide by purging the praetorian guard and fi lling it with soldiers
from the Rhine legions who had acclaimed him and escorted him to Rome.
Vespasian, the last of the four emperors, followed suit after the defeat of
Vitellius, promoting his own followers into the guard. He took the
remarkable further step of appointing as prefect of the guard Titus, his son,
a senator. Commanders of the praetorian guard from the fi rst had been very
deliberately selected from the equestrian order (the ‘second aristocracy’)
rather than from the senate. The next usurper to found a dynasty, Septimius
Severus, fi lled the praetorian guard with the Danubian troops who had
carried him to power (in 193). He also stationed two loyal legions just
outside Rome.
Vespasian, founder of the Flavian dynasty (69–96), was thought to be a
better prospect as emperor than his various civil- war rivals because he had
two sons. In fact continuity and uncontested successions did ensue, as
Vespasian was followed by fi rst Titus and then Domitian. The reign of
Domitian eventually collapsed as relations with the senate, which were
never easy, turned sour and he was murdered in a palace plot. In the vacuum,
the senator Nerva, elderly and childless, emerged as emperor. To save his
fl agging regime he had recourse to adoption, and outside the family. His
choice was a wise one, if forced: he turned, in 98, to the commander of the
nearest large army, the three legions of Upper Germany, Trajan.^7
Thereafter, for the best part of a century, adoption was the regular way of
arranging the succession, paving the way for the reigns of Hadrian,
Antoninus Pius and Marcus Aurelius, who made his adoptive brother Lucius
Verus co- ruler (in 161) in accordance with Hadrian’s wishes. However the
hereditary principle had not lost its magnetic attraction for Roman emperors.
Marcus Aurelius produced a son who would survive him, Commodus, and
automatically prepared him for the succession, making him co- emperor (in
177). In so doing he brought to an abrupt end a sequence of worthy