Parthians, the Scythians, the Teutons and the like, or driving them before them.
Never at any time did the Romans succeed in pushing their empire beyond Mesopotamia, and upon Mesopotamia their hold was never very secure. Before the close of the republic that power of assimilation which had been the secret of their success was giving way to "patriotic" exclusiveness and "patriotic" greed. Rome plundered and destroyed Asia Minor and Babylonia, which were the necessary basis for an eastward extension to India, just as she had destroyed and looted Carthage and so had no foothold for extension into Africa, and just as she had destroyed Corinth and so cut herself off from an easy way into the heart of Greece. Western European writers, impressed by the fact that later on Rome Romanized and civilized Gaul and South Britain and restored the scene of her earlier devastations in Spain to prosperity, are apt to ignore that over far greater areas to the south and east her influence was to weaken and so restore to barbarism the far wider conquests of Hellenic civilization.
But among the politicians of Italy in the first century B.C. there were no maps of Germany and Russia, Africa and central Asia, and no sufficient intelligence to study them had they existed. Rome never developed the fine curiosities that sent Hanno and the sailors of Pharaoh Necho down the coasts of Africa. When, in the first century B.C., the emissaries of the Han dynasty reached the eastern shores of the Caspian Sea, they found only stories of a civilization that had receded. The memory of Alexander still lived in these lands, but of Rome men only knew that Pompey had come to the western shores of the Caspian and gone away again, and that Crassus had been destroyed. Rome was preoccupied at home. What mental energy remained over in the Roman citizen from the attempt to grow personally rich and keep personally safe was intent upon the stratagems and strokes and counter-strokes of the various adventurers who were now manifestly grappling for the supreme power.
It is the custom of historians to treat these struggles with extreme respect. In particular the figure of Julius Cæsar is set