Central Europe is the belt between the German lands and the Russian plain, and its religious history begins with a question about language. In 863 the Byzantine emperor sent two brothers from Thessalonica, Constantine, later called Cyril, and Methodius, to Moravia at the request of its ruler. They devised an alphabet for the Slavonic speech of the region and translated the liturgy and the scriptures into it, which put them at odds with the Frankish clergy already working there, who held that worship belonged in Hebrew, Greek and Latin only. The brothers took the case to Rome and won permission; after their deaths their pupils were driven out and carried the Slavonic books south and east instead.
The consequence was enormous and mostly fell outside the region. Old Church Slavonic became the liturgical language of Bulgaria, Serbia and eventually Russia, so the alphabet devised for Moravia ended by carrying Orthodox Christianity across eastern Europe, while Moravia itself finished in the Latin sphere.
The second great argument in the region also concerned who could say what, and in what language. Jan Hus, a Prague preacher, was condemned at the Council of Constance and burned in 1415 despite a safe conduct, and the Hussite wars that followed produced one of the earliest large-scale challenges to Roman authority in Europe, more than a century before Luther.