found to his cost, for working out a definite plan of conquest.  From Rome, astride of the Tiber, armies could operate on “interior lines” against any combination—­could strike north, east, and south at the same moment.  With Latium faithful behind her she could not be taken in the rear; the unconquerable Hannibal did indeed approach her once on that side, but fell away again like a wave on a rocky shore.  From the sea no enemy ever attempted to reach her till Genseric landed at Ostia in A.D. 455.

Thus it is not difficult to understand how Rome came to be the leading city of Latium; how she came to work her conquering way into Etruria to the north, the land of a strange people who at one time threatened to dominate the whole of Italy; how she advanced up the Tiber valley and its affluents into the heart of the Apennines, and southward into the Oscan country of Samnium and the rich plain of Campania.  A glance at the map of Italy will show us at once how apt is Livy’s remark that Rome was placed in the centre of the peninsula.[6] That peninsula looks as if it were cleft in twain by the Tiber, or in other words, the Tiber drains the greater part of central Italy, and carries the water down a well-marked valley to a central point on the western coast, with a volume greater than that of any other river south of the Po.  A city therefore that commands the Tiber valley, and especially the lower part of it, is in a position of strategic advantage with regard to the whole peninsula.  Now Rome, as Strabo remarked, was the only city actually situated on the bank of the river; and Rome was not only on the river, but from the earliest times astride of it.  She held the land on both banks from her own site to the Tiber mouth at Ostia, as we know from the fact that one of her most ancient priesthoods[7] had its sacred grove five miles down the river on the northern bank.  Thus she had easy access to the sea by the river or by land, and an open way inland up the one great natural entrance from the sea into central Italy.[8] Her position on the Tiber is much like that of Hispalis (Seville) on the Baetis, or of Arles on the Rhone, cities opening the way of commerce or conquest up the basins of two great rivers.  In spite of some disadvantages, to be noticed directly, there was no such favourable position in Italy for a virile people apt to fight and to conquer.  Capua, in the rich volcanic plain of Campania, had far greater advantages in the way of natural wealth; but Capua was too far south, in a more enervating climate, and virility was never one of her strong points.  Corfinium, in the heart of the Apennines, once seemed threatening to become a rival, and was for a time the centre of a rebellious confederation; but this city was too near the east coast—­an impossible position for a pioneer of Italian dominion.  Italy looks west, not east; almost all her natural harbours are on her western side; and though that at Ostia, owing to the amount of silt carried down by the Tiber, has never been a good one, it is the only port which can be said to command an entrance into the centre of the peninsula.