The terror of the Roman arms added weight and dignity to the moderation of the emperors.

They preserved peace by a constant preparation for war; and while justice regulated their conduct, they announced to the nations on their confines, that they were as little disposed to endure, as to offer an injury.

The military strength, which it had been sufficient for Hadrian and the elder Antoninus to display, was exerted against the Parthians and the Germans by the emperor Marcus.

The hostilities of the barbarians provoked the resentment of that philosophic monarch, and, in the prosecution of a just defence, Marcus and his generals obtained many signal victories, both on the Euphrates and on the Danube.

[29] The military establishment of the Roman empire, which thus assured either its tranquillity or success, will now become the proper and important object of our attention.
[Footnote 29: Dion, l.lxxi.Hist.August.in Marco.