Pope (1243-1254). Sinibaldo Fieschi, born around 1190, was elected pope as Innocent IV in June 1243 after an interregnum that, apart from the short pontificate of Celestine IV, had lasted since the death of Pope Gregory IX in August 1241.
From Gregory, Innocent inherited a continuing political confrontation with the Holy Roman Emperor and king of Sicily, Frederick II, as well as a crusading policy that targeted the Orthodox Russians. Innocent was, however, the first pope to seriously face the challenge posed by the Mongol onslaught on western Europe in the course of 1241. After the First Council of Lyons (1245), Innocent sent envoys to the Mongols in order to explore the possibilities of either converting them or turning them into allies of the crusading movement. One of these envoys, John of Plano Carpini, also negotiated with Russian princes over church union with Rome. As both Daniel Romanovich of Galicia-Volhynia and Yaroslav II, grand prince of Vladimir, seemed to respond positively, Innocent abandoned the idea of an alliance with the Mongols and aimed instead to form a grand alliance against them that would include the Russians. In January 1248 Innocent circulated letters to Daniel and to Yaroslav’s son Alexander Yaroslavich (Nevskii), with copies to the master of the Teutonic Order in Prussia; he urged them to warn him through the Teutonic master of impending Mongol attacks on Christianity and to unite under papal protection in the defense against the Mongols. Both Russian princes accepted the proposal. In 1250 Alexander’s brother, Grand Prince Andrei, joined Innocent’s alliance when he married Daniel’s daughter, and in 1251 even the pagan Lithuanian prince Mindaugas accepted baptism. All eastern European rulers still not under Mongol domination had now joined Innocent’s alliance.
Soon, however, this alliance began to dissolve because Innocent was unable to match his diplomacy with military forces that would enable the Russians and Lithuanians to withstand Mongol attacks. In 1253 he tried to salvage the alliance by offering royal crowns to Mindaugas and Daniel. They, in turn, established mutual marital links. However, both succumbed to Mongol attacks in the following years: the church union broke up and Lithuania returned to paganism.