It is easier, perhaps, to describe the growth of Rome from the early Kings to Augustus, than to account for the change from the Rome of the Empire at the beginning of our era to the Rome of the Popes in the year eight hundred. Probably the easiest and truest way of looking at the transition is to regard it according to the periods of supremacy, decadence and ultimate disappearance from Rome of the Roman Army. For the Army made the Emperors, and the Emperors made the times. The great military organization had in it the elements of long life, together with all sudden and terrible possibilities. The Army made Tiberius, Caligula, Claudius and Nero, the Julian Emperors; then destroyed Nero and set up Vespasian after one or two experiments. The Army chose such men as Trajan and Marcus Aurelius, and such monsters as Domitian and Commodus; the Army conquered the world, held the world and gave the world to whomsoever it pleased. The Army and the Emperor, each the other's tool, governed Rome for good and ill, for ill and good, by fear and bounty and largely by amusement, but ultimately to their own and Rome's destruction. For all the time the two great adversaries of the Empire, the spiritual and material, the Christian and the men of the North, were gaining strength and unity. Under Augustus, Christ was born. Under Augustus, Hermann the German chieftain destroyed Varus and his legions. By sheer strength and endurance, the Army widened and broadened the Empire, forcing back the Northmen upon themselves like a spring that gathers force by tension. Unnoticed, at first, Christianity quietly grew to power. Between Christians and Northmen, the Empire of Rome went down at last, leaving the Empire of Constantinople behind it. The great change was wrought in about five hundred years, by the Empire, from the City of the Republic to what had become the City of the Middle Age; between the reign of Augustus, first Emperor, and the deposition of the last Emperor, Romulus Augustulus, by Odoacer, Rome's hired Pomeranian general.