He made a campaign against the Gauls, who had settled in Galatia about a century before, and had become wealthy by means of constant plunderings.

The excuse for the campaign was, that they had served in the Syrian army; the reason was, their wealth, and the ambition of the Consul for glory.
The Galatians were easily overcome, their wealth seized, and they themselves became assimilated to their neighbors.

This war is noticeable chiefly for the reason that Manlius undertook it _without the authority of the Senate_, the first instance of its kind, and a precedent which was too frequently followed in later times.

On his return to Rome he was allowed a triumph, which stamped his act as legal.
These wars in the East brought to Rome immense riches, which laid the foundation of its Oriental extravagance and luxury, and finally undermined the strength of the state.

From Greece were introduced learning and refinement, from Asia immorality and effeminacy.