us. Gibbon has noted an important difference between the civil wars of this period and those of modern Europe. The last have been long and protracted, fought out with all the obstinacy which naturally accompanies the vindication of some great and important principle. The cause of religion or of freedom has been usually involved in them. Not so with these wars of the Roman empire. They were fought not between nations and peoples, but merely between generals and soldiers. As Gibbon says, "The Romans, after the fall of the republic, combated only for the choice of masters." In such struggles, the provinces, and mankind generally, were but uninterested spectators, and cared very little for the result. Hence these wars, unlike those of modern days, were very brief, and one or two battles decided them. The successes of Severus were rapid and complete. Having crossed the Hellespont into Asia with part of his army, he utterly defeated Niger near Issus, where more than five centuries before Alexander had won his second great victory over Dareius. But his work was not yet done. Niger was a man who inspired respect and might be thought worthy of empire. There were those who still clung to him. One city was faithful to his cause, and put forth all its powers of resistance. It was Byzantium. The city may have felt that it had a right to become the head of an Eastern empire.
It seems that the Byzantines may not unreasonably have been confident in their ability to sustain a siege. Their fortifications were the admiration of the world, and their strong and lofty walls, we are told, were so
