Birger was purportedly the son of a female heiress of the Sverker dynasty, thus having royal blood. Eastward expansion Sweden had a certain presence in south-western Finland by the early 13th century, although it is unclear to what extent this translated into political power. A bishopric existed in Nousiainen and later Turku (Åbo), which stood under the papal legate of the Baltic region. The Erikskrönikan contains a graphic description of a military expedition to Tavastia further to the east that King Eric dispatched in an unspecified year, possibly in 1238–39 or 1249–50. While not literally a crusade, the professed aim was to Christianize still pagan lands. A sizable fleet was assembled under the leadership of Birger and sailed over to Tavastia (a problematic statement since Tavastia is an inland region). According to the highly propagandist chronicle, the expedition was an unqualified success: They took their banners and went ashore, The Christians were successful in the war. They let their shields shine all over the land, and so their helmets. They were keen to try their swords on the pagan Tavasts As I expect, they achieved gold and silver and large herds. The Tavasts then ran and were gone, the pagans lost and the Christians won. Anyone who wanted to serve them, and become Christian and accept baptism, they allowed to keep goods and life, and to live in peace without further strife. To any pagan who would not do that, they administered death. The expedition led to the establishment of a permanent fortress, Tavasteborg, and the formal Christianization of the region. As the chronicle has it, "I think the Russian king lost it". The enterprise is not mentioned in other sources, and its circumstances are hotly debated among modern historians. It is possibly connected to a Swedish foray in the Novgorod Republic in 1240. A fleet of ships commanded by a certain Spiridon and accompanied by a few bishops went up the Neva River, but were attacked and routed by the Novgorodian prince Alexander Nevsky. Details of the battle are partly legendary, and its significance might have been exaggerated in Russian historiography. According to a 14th-century source, the Swedish leader was a Belgerd, corresponding to Birger, though this may be a later construction. Renewed domestic feuding Internal fighting once again broke out in 1247, shortly before (or possibly after) Ulf Fase's death. The Folkung Party warred with King Eric and