When Constantine the Great transferred the seat of his empire from Rome to Byzantium he not only preserved that empire from destruction, but he established it at a centre from whence it derived new life and energy. Menaced by the barbarians from the north and the Persians from the east, the empire was in constant danger of overthrow. Now it is often of the greatest importance rather to anticipate an attack than to await its onslaught, rather to be ready for your enemy near his gates than to await his arrival at yours. Constantine therefore removed his base of operations nearer to the source of danger and established himself at the very gate of his enemies. At New Rome new conditions of life had to be faced; new methods of building, suitable to the climate, the skilled labour, and to the materials available, had to be devised. But in the very solution of these difficulties lay the germs of salvation. By his bold and sagacious action a new life and vigour was infused into his people, a new force which not only preserved the empire for over eleven hundred years, but maintained a progressive civilization during what was probably one of the darkest periods in the history of the world. But it was in the selection of the particular site that the emperor showed the greatest prescience. At Byzantium he commanded the great line of communication between east and west through Asia Minor and Thrace, and also controlled the maritime passage between the Euxine and the Propontis, the Straits of Bosporus. He secured at once the most potentially wealthy and the most strongly situated position in Eastern Europe.