Byzantium and the west (chiefly the Germans) were both launching great missionary ventures among the Slavs.' The two lines of missionary advance, from the east and from the west, soon converged; and when Greek and German missionaries found themselves at work in the same land, it was difficult to avoid a conflict, since the two missions were run on widely different principles. The clash naturally brought to the fore the question of the Filioque, used by the Germans in the Creed, but not used by the Greeks. The chief point of trouble was Bulgaria, a country which Rome and Constantinople alike were anxious to add to their sphere of jurisdiction. The Khan Boris was at first inclined to ask the German missionaries for baptism: threatened, however, with a Byzantine invasion, he changed his policy and around 865 accepted baptism from Greek clergy. But Boris wanted the Church in Bulgaria to be independent, and when Constantinople refused to grant autonomy, he turned to the west in hope of better terms. Given a free hand in Bulgaria, the Latin missionaries promptly launched a violent attack on the Greeks, singling out the points where Byzantine practice differed from their own: married clergy, rules of fasting, and above all the Filioque. At Rome itself the Filioque was still not in use, but Nicolas gave full support to the Germans when they insisted upon its insertion in Bulgaria. The Papacy, which in 808 had mediated between the Franks and the Greeks, was now neutral no longer.
