Mediæval conversion to Christianity was, as a rule, tribal, or national, rather than individual, or personal, and consequently it took some time before satisfactory fruitage was noticeable in the lives of the people. But it was a great victory to substitute the Christian for the pagan ideal. The agencies employed to carry out this process of conversion were: (1) missionaries, mostly Latin, Celtic, English, German, Greek, and Slavic monks; (2) the sword in the hands of a stern ruler; (3) the marriage of Christian women to pagan kings and princes; and (4) the recognised superiority of Christianity, Christian institutions, and Christian nations. It must be borne in mind, likewise, that some of the German tribes settled in the very heart of Christendom where Christian influences could operate directly and immediately. The earliest successful conversion of the Teutons was to Arianism. That work was begun at least as early as the time of Constantine, because a Gothic bishop sat in the Council of Nicæa (325). Bishop Ulfilas (d. 381), the "Apostle to the Goths," called by Constantine the Great "the Moses of the Goths,"[232:1] translated the Bible into Gothic[232:2] and won his countrymen to Arianism. St. Chrysostom in 404 established in Constantinople a school for the training of Gothic missionaries.[232:3] The Ostrogoths, Visigoths, Burgundians, and Vandals all embraced that faith. But the fervent and more aggressive missionary zeal of Rome gradually replaced Arianism in western Europe with orthodox Christianity--the Burgundians in 517, the Suevi in 550, the Visigoths in 587, the Lombards, the last stronghold of Arianism in the West, in the eighth century. The unparalleled missionary activity of the Roman Church was due of course primarily to religious enthusiasm, but other causes must also be taken into account. As a matter of self-preservation to protect herself from the inveterate paganism of the ancient world, on the one hand, and from the torrent of barbaric invaders, on the other, the conflict was thrust upon Rome and she must conquer or perish. Again the development of the hierarchy along the lines of the Petrine theory made it imperative that Rome should win and rule the West. The wise policy of winning kings first and nations afterwards was simply adopted from Roman imperial practice but it was eminently successful. It likewise enabled the Pope of Rome to control all missionary enterprise from his ecclesiastical capital, and to employ it for the further extension of the papal prerogative.