Tacitus two or three times observes that the western provinces of the Empire looked out on no other land to the westward and bordered on no free nations.

That is one half of a larger fact which influenced the whole history of the Empire.

Round the west lay the sea and the Sahara.

In the east were wide lands and powerful states and military dangers and political problems and commercial opportunities.

The Empire arose in the west and in Italy, a land that, geographically speaking, looks westward.