Hannibal was ill supplied from home. The Roman militia, being continually in the field, became in the progress of the war a well disciplined and well-exercised standing army, and the superiority of Hannibal grew every day less and less. Hasdrubal judged it necessary to lead the whole, or almost the whole of the standing army which he commanded in Spain, to the assistance of his brother in Italy. In this march he is said to have been misled by his guides, and in a country which he did not know, was surprised and attacked by another standing army, in every respect equal or superior to his own, and was entirely defeated.

When Hasdrubal had left Spain, the great Scipio found nothing to oppose him but a militia inferior to his own. He conquered and subdued that militia, and, in the course of the war, his own militia necessarily became a well-disciplined and well-exercised standing army. That standing army was afterwards carried to Africa, where it found nothing but a militia to oppose it. In order to defend Carthage it became necessary to recall the standing army of Hannibal. The disheartened and frequently defeated African militia joined it, and, at the battle of Zama, composed the greater part of the troops of Hannibal. The event of that day determined the fate of the two rival republics.

From the end of the second Carthaginian war till the fall of the Roman republic, the armies of Rome were in every respect standing armies. The standing army of Macedon made some resistance to their arms. In the height of their grandeur it cost them two great wars, and three great battles, to subdue that little kingdom, of which the conquest would probably have been still more difficult had it not been for the cowardice of its last king. The militias of all the civilised nations of the ancient world, of Greece, of Syria, and of Egypt, made but a feeble resistance to the standing armies of Rome. The militias of some barbarous nations defended themselves much better. The Scythian or Tartar militia, which Mithridates drew from the countries north of the Euxine and Caspian seas, were the most formidable enemies whom the Romans had to encounter after the second Carthaginian war. The Parthian and German militias, too, were always respectable, and upon several occasions gained very considerable advantages over the Roman armies. In general, however, and when the Roman armies were well commanded, they appear to have been very much superior; and if the Romans did not pursue the final conquest either of Parthia or Germany, it was probably because they judged that it was not worth while to add those two barbarous countries to an empire which was already too large. The ancient Parthians appear to have been a nation of Scythian or Tartar extraction, and to have always retained a good deal of the manners of their ancestors. The ancient Germans were, like the Scythians or Tartars, a nation of wandering shepherds, who went to war under the same chiefs whom they were accustomed to follow in peace. Their militia was exactly of the same kind with that of the Scythians or Tartars, from whom, too, they were probably descended.

Many different causes contributed to relax the discipline of the Roman armies. Its extreme severity was, perhaps, one of those causes. In the days of their grandeur, when no enemy appeared capable of opposing them, their heavy armour was laid aside as unnecessarily burdensome, their labourious exercises were neglected as unnecessarily toilsome. Under the Roman emperors, besides, the standing armies of Rome, those particularly which guarded the German and Pannonian frontiers, became dangerous to their masters, against whom they used frequently to set up their own generals. In order to render them less formidable, according to some authors, Dioclesian, according to others, Constantine, first withdrew them from the frontier, where they had always before been encamped in great bodies, generally of two or three legions each, and dispersed them in small bodies through the different provincial towns, from whence they were scarce ever removed but when it became necessary to repel an invasion. Small bodies of soldiers quartered, in trading and manufacturing towns, and seldom removed from those quarters, became themselves tradesmen, artificers, and manufacturers. The civil came to predominate over the military character, and the standing armies of Rome gradually degenerated into a corrupt, neglected, and undisciplined militia, incapable of resisting the attack of the German and Scythian militias, which soon afterwards invaded the western empire. It was only by hiring the militia of some of those nations to oppose to that of others that the emperors were for some time able to defend themselves. The fall of the western empire is the third great revolution in the affairs of mankind of which ancient history has preserved any distinct or circumstantial account. It was brought about by the irresistible superiority which the militia of a barbarous has over that of a civilised nation; which the militia of a nation of shepherds has over that of a nation of husbandmen,