Slavonic worship, rival councils, and debates over the Lord’s Supper

Unknown illuminator at Tours, about 849–851. Christ with the four Evangelist symbols, from the Gospels of Lothair.
Worship in a known language, and Baptism of rulers.
Christ in the Supper, and predestination
Five councils, and two claims to be the eighth.
Missionaries, patriarchs, popes, and monks
Empire, learning, and print in the same century

How the Lutheran Confessions judge these debates
Why does winning a church fight not prove a doctrine right?