en
weakened to reinforce the Syrian troops in the Parthian war and this
enabled the barbarians to penetrate the frontier defences and ravage
Noricum and Pannonia as far as Aquileia at the head of the Adriatic. The
two Augusti proceeded to the scene of war, and after a protracted struggle
in which Dacia suffered from a hostile invasion, the enemy were forced to
make peace. The Marcomanni submitted in 172, and the Quadi and Sarmatians
in 175 A. D. They were forced to surrender the prisoners carried off from
the Roman provinces, over 160,000 in number, and to furnish military aid
to Rome, while large numbers of them were settled on waste lands south of
the Danube under the obligation of tilling the soil and rendering military
service. The Roman victory was commemorated by the erection of a column at
Rome with sculptures picturing incidents of the war, in imitation of
Trajan's memorial. In addition to the prosecution of this war, the
strength of the empire had been taxed by serious outbreaks in Mauretania,
Gaul and Egypt.

*Revolt of Avidius Cassius, 175 A. D.* The complete subjugation of the
northern foe was hindered by the revolt of Avidius Cassius, the general
who had distinguished himself in the Parthian war and had suppressed the
revolt in Egypt. Verus, the colleague of Aurelius, had died in 169, and at
a rumor of the death of Aurelius himself in 175 A. D., Cassius proclaimed
himself Imperator in Syria. Thereupon Aurelius hastened to conclude peace
with the Sarmatians and proceeded to the East. Upon his arrival he found
that Cassius had been killed by his own soldiers. Soon afterwards
Commodus, the son of Aurelius, received the title Augustus and became
co-ruler with his father (177 A. D.).

*Second war with the Marcomanni and Quadi, 177-180 A. D.* In 177 A. D. war
broke out anew with the Quadi and Marcomanni. Aurelius again took command
on the Danube and after two years' fighting had won so complete a victory
that he contemplated the annexation of the region occupied by these
peoples. But for a second time he was robbed of the fruits of his toil, on
this occasion by the hand of death, 17 March, 180 A. D. The principate
passed to his son and colleague, Commodus.

*Lucius Aurelius Commodus, **sole princeps**, 180-192 A. D.* Lucius
Aurelius Commodus, the ignoble son of a noble father, is one of the few in
the long line of Roman rulers of whom nothing good can be said. Cowardly,
cruel and sensual, he gave himself up to