Lucius Verus was co-emperor with Marcus Aurelius. As a junior, Lucius Verus went of to war to fight the Parthians, while Marcus Aurelius remained in Rome. In 163, Lucius Verus reconquered Armenia from the Parthians.
The Romans invaded Mesopotamia in 163, making major headway in 165 with the conquest of Osroene, Nisibis, Ctesiphon and in 166 with parts of Media.
Peace came in 167, when Nisibis was ceded to the Roman Empire.
In 166, the Marcomannic Wars started, with incursions of the northern neighbours into the roman Empire along the Danube river. Marcus Aurelius and Lucius Verus went north to fight them. Lucius Verus died in 169 at the Danube borders.