Both had become pacific.

It is a well-known fact that Augustus left it as a principle of policy to his successors that the Roman Empire had reached its proper limits, and could not with advantage be extended further.

This principle, followed with the utmost strictness by Tiberius, was accepted as a rule by all the earlier Caesars, and only regarded as admitting of rare and slight exceptions.

Trajan was the first who, a hundred and thirty years after the accession of Augustus, made light of it and set it at defiance.

With him re-awoke the spirit of conquest, the aspiration after universal dominion.