The conception early developed in the Church that the spread of God's Kingdom on earth was a warfare. That idea was founded on the words of Jesus,[230:1] on the assertions of the Apostles, and on the sacrifices of the early martyrs. Monasticism made this conviction peculiarly personal. The organised Church asserted it on every occasion. The conversion of the barbarians was viewed, in a broad sense, as an invasion and a conquest. It was a campaign with all western Europe as its field. In time it covered six centuries or more. The generals, the able strategists, were the competent and zealous Roman pontiffs, and the subordinate officers were emperors, kings, princes, bishops, and abbots. The army was that great host of devoted monks, of consecrated priests, and earnest Christian laymen. The weapons in the hands of these conquerors were Christian love and sympathy. They were driven on by an irresistible zeal for saving souls. They were clothed in the power of poverty, austerity, suffering, obedience, and self-denial. The conflict was one which, in its outcome, was to shape the destiny of the world. The man above all others who was carried away by this dream of duty for the Church militant in winning those outside the true Church to membership, was the monk-Pope, Gregory the Great. Pagan Rome had failed to make a complete and permanent conquest of the barbarians. Christian Rome, inspired by this master spirit, was to succeed in conquering both the bodies and the souls of the barbarians, and to use them for her own glory. When Gregory the Great died in 604, Christendom practically covered the Roman Empire and at certain points extended beyond it. Those who bore the name Christian included Jews, Romans, Greeks, Celts, and Germans. The Christian world was already divided into two great branches--the Eastern, or Greek Church, and the Western, or Roman Church,--which were becoming more and more pronounced in their differences. The Christian missionary work, from the sixth to the twelfth century, must be viewed broadly as a process of civilisation, since the missionaries carried with them intellectual light, as well as spiritual truth, and paved the way for law and justice. They opened up channels through which the higher ideals and better institutions of the south might work northward to revolutionise agriculture, trade, social life, and general economic conditions. "The experience of all ages," said Neander, "teaches us that Christianity has only made a firm and living progress, where from the first it has brought with it the seeds of all human culture, although they have only been developed by degrees."[231:1]