152 THE HISTORY OF MEDIEVAL EUROPE Some of the Greek cities, however, remained undestroyed amid all these waves of invasion and kept up their trade with Constantinople. Christianity was spread among the Serbians and Croatians by Latin-speaking clergy in the period from 642 to 731. This conversion, however, was superficial and Conversion . of the Bal- the church service in Latin took slight hold upon an peop es ^ masses. It was only when the Scriptures were translated into a Slavonic version by the two brothers, Constantine (or Cyril) and MeJ^odius, and when the liturgy also was put into Slavic, that Christianity really be- came the religion of the people. This occurred in the second half of the ninth century under the auspices of the Eastern Church. The Croatians, however, soon returned to their allegiance to the Papacy. In 864, the Bulgarian monarch, Boris I, was converted to Christianity, and, after some vacil- lation between the Eastern Church and the Church of Rome, finally adhered to the former. He later abdicated in order to enter a monastery. The first Serbian churches were hardly big enough to hold the priest and altar; the people stood outside in the churchyard, which also served as a cemetery. Though the campaigns of Heraclius did not permanently save Jerusalem and his eastern provinces, we must not be- Service ren- ^^ e his achievement. For he probably did save dered by Constantinople, which might not have held out nople to " had he abandoned it in the depths of its adver- European s jty. As it was, that great city was to endure for civilization . ° J centuries to come, was to serve as a protection to western Europe from attacks from the east, was to set an example of superior civilization to a barbarous world about it in both East and West, was to be a center whence Christian missions would radiate, a preserve for classical culture and Christian art, a mart of trade, a spring of busi- ness life in the midst of general economic stagnation. To a certain extent the ancient city, if not the ancient city- state, lived on in Constantinople; but in many respects its life and culture had been essentially altered by Chris-
