Antoninus Pius died A.D. 161. The Senate, it is said, urged M. Antoninus to take the sole administration of the empire, but he associated with himself the other adopted son of Pius, L. Ceionius Commodus, who is generally called L. Verus. Thus Rome for the first time had two emperors. Verus was an indolent man of pleasure, and unworthy of his station. Antoninus however bore with him, and it is said that Verus had sense enough to pay to his colleague the respect due to his character. A virtuous emperor and a loose partner lived together in peace, and their alliance was strengthened by Antoninus giving to Verus for wife his daughter Lucilla. The reign of Antoninus was first troubled by a Parthian war, in which Verus was sent to command; but he did nothing, and the success that was obtained by the Romans in Armenia and on the Euphrates and Tigris was due to his generals. This Parthian war ended in A.D. 165. Aurelius and Verus had a triumph (A.D. 166) for the victories in the East. A pestilence followed, which carried off great numbers in Rome and Italy, and spread to the west of Europe. The north of Italy was also threatened by the rude people beyond the Alps from the borders of Gallia to the eastern side of the Hadriatic. These barbarians attempted to break into Italy, as the Germanic nations had attempted near three hundred years before; and the rest of the life of Antoninus, with some intervals, was employed in driving back the invaders. In A.D. 169 Verus suddenly died, and Antoninus administered the state alone. During the German wars Antoninus resided for three years on the Danube at Carnuntum. The Marcomanni were driven out of Pannonia and almost destroyed in their retreat across the Danube; and in A.D. 174 the emperor gained a great victory over the Quadi. In A.D. 175, Avidius Cassius, a brave and skilful Roman commander who was at the head of the troops in Asia, revolted and declared himself Augustus. But Cassius was assassinated by some of his officers, and so the rebellion came to an end. Antoninus showed his humanity by his treatment of the family and the partisans of Cassius; and his letter to the Senate, in which he recommends mercy, is extant.