Abstract
During the 13th century the Papal Curia made first steps to revive the ecclesiastical unity between Western and Eastern Christendom. At the Council of Lyon in 1245 the papacy presented the idea of assisting Russian princes against the Mongolian conquerors.
However, this plan was tied to a rather fantastical project of a Catholic mission to Orthodox Russians which would have enabled mending of the East-West Schism. In addition, the Russian principalities were to fulfil the role of a defensive barrier intended to prevent another Mongolian invasion to the West.
While Daniil Romanovich, the Prince of Galicia-Volhynia, accepted Pope's offer, temporarily converted to Catholicism and was subsequently crowned a king, Alexander Yaroslavich, the prince of Novgorod and subsequently grand prince of Vladimir, denied a similar offer of pope Innocent IV to become a Catholic. This stemmed from different political situations which their respective domains experienced.