8. Although the Roman Empire remained one in law, government, and culture until the Germans came in sufficient force to conquer the western portions of it, a tendency may nevertheless be noticed some time before the conquest for the eastern and western portions to drift apart. Constantine, who established his supremacy only after a long struggle with his rivals, hoped to strengthen the vast state by establishing a second capital, which should lie far to the east and dominate a region very remote from Rome. Constantinople was accordingly founded in 330 on the confines of Europe and Asia.[8] This was by no means supposed to destroy the unity of the Empire. Even when Theodosius the Great arranged (395) that both his sons should succeed him, and that one should rule in the West and one in the East, he did not intend to divide the Empire. It is true that there continued to be thereafter two emperors, each in his own capital, but they were supposed to govern one empire conjointly and in "unanimity." New laws were to be accepted by both. The writers of the time do not speak of two states but continue to refer to "the Empire," as if the administration were still in the hands of one ruler. Indeed the idea of one government for all civilized mankind did not pass away but continued to influence men during the whole of the Middle Ages. Although it was in the eastern part of the Empire that the barbarians first got a permanent foothold, the emperors at Constantinople were able to keep a portion of the old possessions of the Empire under their rule for centuries after the Germans had completely conquered the West. When at last the eastern capital of the Empire fell, it was not into the hands of the Germans, but into those of the Turks, who have held it since 1453. There will be no room in this volume to follow the history of the Eastern Empire, although it cannot be entirely ignored in studying western Europe. Its language and civilization had always been Greek, and owing to this and the influence of the Orient, its culture offers a marked contrast to that of the Latin West, which was adopted by the Germans. Learning never died out in the East as it did in the West, nor did art reach so low an ebb. [Sidenote: Constantinople the most wealthy and populous city of Europe during the early Middle Ages.] For some centuries after the disruption of the Roman Empire in the West, the capital of the Eastern Empire enjoyed the distinction of being the largest and most wealthy city of Europe. Within its walls could be found the indications of a refinement and civilization which had almost disappeared in the Occident. Its beautiful buildings, its parks and paved streets, filled the traveler from the West with astonishment. When, during the Crusades, the western peoples were brought into contact with the learning and culture of Constantinople they were greatly and permanently impressed by them.