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War with Germanic tribes (166–180)

During the early 160s, Fronto's son-in-law Victorinus was stationed as a legate in Germany. He was there with his wife and children (another child had stayed with Fronto and his wife in Rome). The condition on the northern frontier looked grave. A frontier post had been destroyed, and it looked like all the peoples of central and northern Europe were in turmoil. There was corruption among the officers: Victorinus had to ask for the resignation of a legionary legate who was taking bribes.

Experienced governors had been replaced by friends and relatives of the imperial family. Lucius Dasumius Tullius Tuscus, a distant relative of Hadrian, was in Upper Pannonia, succeeding the experienced Marcus Nonius Macrinus. Lower Pannonia was under the obscure Tiberius Haterius Saturnius. Marcus Servilius Fabianus Maximus was shuffled from Lower Moesia to Upper Moesia when Marcus Iallius Bassus had joined Lucius in Antioch. Lower Moesia was filled by Pontius Laelianus's son. The Dacias were still divided in three, governed by a praetorian senator and two procurators. The peace could not hold long; Lower Pannonia did not even have a legion.

Starting in the 160s, Germanic tribes, and other nomadic people launched raids along the northern border, particularly into Gaul and across the Danube. This new impetus westwards was probably due to attacks from tribes further east. A first invasion by the Chatti in the province of Germania Superior was repulsed in 162.

Far more dangerous was the invasion of 166, when the Marcomanni of Bohemia, clients of the Roman Empire since AD 19, crossed the Danube together with the Lombards and other Germanic tribes. Soon thereafter, the Iranian Sarmatian Iazyges attacked between the Danube and the Theiss rivers.

The Costoboci, coming from the Carpathian area, invaded Moesia, Macedonia, and Greece. After a long struggle, Marcus managed to push back the invaders. Numerous members of Germanic tribes settled in frontier regions like Dacia, Pannonia, Germany, and Italy itself. This was not a new thing, but this time the numbers of settlers required the creation of two new frontier provinces on the left shore of the Danube, Sarmatia and Marcomannia, including today's Czech Republic, Slovakia, and Hungary. Some Germanic tribes who settled in Ravenna revolted and managed to seize possession of the city. For this reason, Marcus decided not only against bringing more barbarians into Italy, but even banished those who had previously been brought there. In 168, the two emperors embarked on a new military campaign, expelling the invading Marcomanni and Quadi from Aquileia. Lucius Verus fell ill and died on his way back Rome, probably due to the plague, in January or February 169.