This was a great achievement that had never happened before, but it also made a lot of difficulties. Take size alone. The Roman Empire was now too big to manage. In those days, you couldn’t fly a general (or a tax collector, or an imperial officer, or the emperor himself) from York, England—that’s where Constantine the Great was when he started toward Rome to become the Roman emperor—to the Persian border in a matter of hours. You couldn’t even put him on a fast train. The Roman roads were famous, but the only way you could travel them was on foot, on horseback, or in a litter or chariot. And from one end of the empire to the other was 3,000 miles! Two centuries after Trajan, an emperor called Diocletian decided to do something about it. Diocletian was the son of a freed slave, but he became the first absolute ruler the Roman Empire ever had. Before that the emperor was merely _princeps_ (from which the English word “prince” is derived), or first citizen. But once Diocletian had all this power, he proceeded to divide it up. He appointed a co-emperor (a second Augustus) with an assistant emperor called a _caesar_ to help him, and put him in charge of the Roman Empire in the West. Diocletian himself, with his own _caesar_, kept the East. Although he was still head emperor and the other emperor was supposed to obey him, the Roman Empire was now divided into two parts. About forty years later, another emperor took an even more important step. Constantine the Great decided that the empire needed a second capital as much as it needed two rulers, and since he was a Christian emperor—actually he was the first Christian emperor—he decided it must be a Christian city. He looked around him carefully. First he thought of Nicomedia (now Ismid in modern Turkey) where Diocletian had had his camp; but it had been the capital of a heathen king. Then he considered ancient Troy, for the Romans were supposed to be descended from the Trojans. He even began to build walls there. But one day somebody reminded him of the ruined city of Byzantium with its wonderful location. “That is the place!” he cried. On foot, with lance in hand and followed by a solemn procession, he marched over pleasant hills and valleys that were still covered with vines and greenery. As they tried to keep up with him his panting courtiers asked him how big he planned to make the place. “I shall walk,” he replied, “until God, my invisible Guide, bids me to halt.”