There can be no doubt that some of the irruptions of the barbarians--particularly those of the Goths into Romelia, which led to the fatal battles of Thessalonica and Adrianople; and of Alaric into Italy, which terminated in the capture of the Eternal City--were very formidable inroads, and might, in the best days of the empire, have taxed its strength and resolution to repel. But a little consideration must be sufficient to show, that, formidable as these invasions were, they could without much difficulty have been withstood, if the empire had possessed the strength which it did in the days of the republic, or in the first two centuries of the Cæsars. The Cimbri and Teutones, whom Marius combated and destroyed on the Rhone and in the north of Italy, were at least as formidable a body of barbarians as those which four centuries afterwards overturned the western empire. The forces whom Cæsar conquered in Gaul, Trajan on the Danube, were to the full as powerful as those which carried the standards of the Goths and Vandals to Athens and Carthage. Ætius, in the decline of the empire, and with the mingled Roman and barbarian force of Gaul alone, defeated Attila in the plenitude of his power, at the head of three hundred thousand men, on the field of Chalons. Belisarius, with fifteen thousand men, recovered Africa from the Vandals; thirty thousand legionary soldiers did the same by Italy under Narses, and overthrew the whole power of the Goths. So high did the Roman soldiers still stand even in the estimation of their enemies, that Totila, the warlike monarch of the Goths, strove to bribe them into his service by offers of high pay. None had yet been approved equal to these legionary soldiers in battle; and the manner in which, with infinitely inferior forces, they repelled the barbarians on all sides, decisively demonstrates this superiority. The vigour and ability of Heraclius so restored the empire, when wellnigh sinking under the might of its enemies, that for a century it was regarded with awe by the barbarous nations all round its immense frontier. The five provinces beyond the Euphrates were conquered by the Romans from the Parthians during the decline of the empire. Nothing is so remarkable, in the last three centuries of Roman history, as the _small number_ of the forces which combated around the Eagles, and the astonishing victories which, when led by ability, they gained over prodigious bodies of their enemies. The legions had dwindled into battalions, the battalions into cohorts. The four hundred and fifty thousand men who under Augustus guarded the frontiers of the empire, had sunk to one hundred and fifty thousand in the time of Justinian.[3] But this hundred and fifty thousand upheld the Eastern empire for a thousand years. So feeble were the assaults of the barbarians, that for above two centuries of that time the single city of Constantinople, with the aid of the Greek fire, defended itself with