Both Scipio and Wellington restored their countrymen's confidence in arms when shaken by a series of reverses, and each of them closed a long and perilous war by a complete and overwhelming defeat of the chosen leader and the chosen veterans of the foe." Neither of these Englishmen mentions the yet more striking coincidence, that in both cases the mastery of the sea rested with the victor.

The Roman control of the water forced Hannibal to that long, perilous march through Gaul in which more than half his veteran troops wasted away; it enabled the elder Scipio, while sending his army from the Rhone on to Spain, to intercept Hannibal's communications, to return in person and face the invader at the Trebia.

Throughout the war the legions passed by water, unmolested and unwearied, between Spain, which was Hannibal's base, and Italy, while the issue of the decisive battle of the Metaurus, hinging as it did upon the interior position of the Roman armies with reference to the forces of Hasdrubal and Hannibal, was ultimately due to the fact that the younger brother could not bring his succoring reinforcements by sea, but only by the land route through Gaul.

Hence at the critical moment the two Carthaginian armies were separated by the length of Italy, and one was destroyed by the combined action of the Roman generals.
On the other hand, naval historians have troubled themselves little about the connection between general history and their own particular topic, limiting themselves generally to the duty of simple chroniclers of naval occurrences.

This is less true of the French than of the English; the genius and training of the former people leading them to more careful inquiry into the causes of particular results and the mutual relation of events.
There is not, however, within the knowledge of the author any work that professes the particular object here sought; namely, an estimate of the effect of sea power upon the course of history and the prosperity of nations.