Second Swedish Crusade

The Second Swedish Crusade was a military expedition by the Kingdom of Sweden into Tavastia c. 1249–1250 as described by the Erikskrönikan. As described by the Erikskrönikan, the Swedes defeated the Tavastians under the leadership of Birger Jarl.

Background
Sweden had held a foothold within Finland, specifically Finland Proper since the First Swedish Crusade. Swedish missionary attempts, possibly having been led by the bishop Thomas, were present within Tavastia in c. 1230. The Tavastian uprising from 1236–1237 led to a justification for the Swedes to invade Tavastia, with Pope Gregory IX calling the Swedes to attack them.

Eric's Chronicle
All details of the crusade are from Eric's Chronicle, which is largely propagandist in nature, written a century after the events, amidst internal unrest and a war against Novgorod. The chronicle says that the crusade took place between the Battle of Sparrsätra in 1247 and the death of King Eric (XI) in 1250, and presents the Tavastians (taffwesta) as the Swedes' opponents. According to the chronicle, the expedition was prepared in Sweden and then conducted over sea to a land on the coast, where the enemy was waiting.

The Chronicle also mentioned that a castle called taffwesta borg was established after the war. The Chronicle also linked the Crusade to a contest with the Orthodox Russians, making a point of the fact that the "Russian king" had now lost the conquered land.

Other sources
The so-called "Detmar Chronicle", originating from Lübeck around the year 1340, confirmed the expedition with a short note that Birger Jarl submitted Finland under Swedish rule. The "Lübeck Chronicle" states that in 1266, Finland become a part of the Kingdom of Sweden.

Interpretations
Unlike the dubious First Swedish crusade, there seems to be little doubt that Sweden's effort to Christianize Finland reached a culmination in the middle of the 13th century. Still, many details, including the year and the exact nature, remain the subject of debate.

Nature of the Crusade
Although the Chronicles attempted to paint the Crusade as a war of conquest, it was likely more of an unusually bloody phase in the ongoing process by which Finland was incorporated in the Swedish state. Sweden had a central government and a strong ideological force in the form of the Catholic church. The Finnish chieftains who joined gained power and prestige.

Dating controversy
According to the Eric's Chronicle the crusade took place between the dates of 1247–1250.

The 1247–1250 date has been viewed as false by Jarl Gallén and Gisela Nordstrandh who view it to be incorrect due to their position that it would only be logical for the crusade to take place following the Tavastian uprising and after the call of Pope Gregory IX to launch a crusade against the Tavastian pagans. They have suggested that the Second Swedish Crusade could only have taken place from 1238–39. Swedish historian Dick Harrison finds the theory of an early crusade most probable, based on the papal letter, which would also make the war a properly sanctioned crusade, and the fact that Sweden was otherwise peaceful during that period. However the 1238-1239 theory has not gained much prevalence or acceptance in studies. Peter Andreas Munch stated that according to the Saga of Haakon Haakonarson, Birger Jarl would have been at the Norwegian border during the summer of 1349 of the Second Crusade.

The position that the crusade took place from 1247–1250 has been defended by Rolf Pipping, who dismisses the work of Peter Andreas Munch, by stating that Birger Jarl did not stay on the Norwegian border in summer, instead in winter, possibly March and that Peter Andreas Munch misinterpreted the saga. The Morkinskinna describes King Magnus Barefoot leaving the Oslofjord at the beginning of spring, which was on Candlemas (February 2) traditionally in Medieval Scandinavia.

Taffwesta borg
The Chronicle mentioned an impressive castle that was built by the Swedes, taffwesta borg. This has been interpreted as either Häme Castle (Swedish Tavastehus) or the nearby Hakoinen Castle, but there is no archaeological evidence at either site to support such an early dating.

Church reaction and reorganization
Probably in an effort to prevent other parties from getting involved in the conflict, Pope Innocent IV took Finland under his special protection in August 1249 but without mentioning Sweden in any way. The bishop of Finland, Thomas, probably a Dominican friar, had resigned already in 1245 and died three years later in a Dominican convent in Gotland. The seat being vacant, the diocese had probably been under the direct command of the papal legate, William of Modena, whose last orders to Finnish priests were given in June 1248.

Bero was eventually appointed as the new bishop in 1248/9, presumably soon after William's visit to Sweden for an important church meeting at Skänninge that ended on 1 March 1248. The so-called "Palmsköld booklet" from 1448 noted that it was Bero who gave the Finns' tax to the Swedish king. Bero came directly from the Swedish court, like his two successors. It seems that Swedish bishops also held all secular power in Finland until the 1280s, when the position of the Duke of Finland was established.

In 1249, the situation was also seen clear enough to establish the first monastery in Finland, a Dominican convent. The convent was next to the bishop's fortification in Koroinen until the end of the century.

Swedish succession
Eric's Chronicle tells of how, as an unexpected side effect, the expedition seems to have cost Birger the Swedish crown. When King Eric died in 1250, Birger was absent from Sweden. The Swedish lords, led by Joar Blå, selected Birger's underaged son Valdemar as the new king, instead of the powerful jarl himself.

Swedish rule in Finland
From 1249 onwards, sources generally regard Finland Proper and Tavastia as a part of Sweden. The Diocese of Finland proper is listed among the Swedish dioceses for the first time in 1253. In the Novgorod First Chronicle, Tavastians (yem) and Finns proper (sum) are mentioned on an expedition with Swedes (svei) in 1256. However, very little is known about the situation in Finland in the following decades. That is partly because Western Finland was now ruled from Turku and so most of the documents remained there. As the Novgorod forces burned the city in 1318 during the Swedish-Novgorodian Wars, very few of the documents about what had happened in the previous century remained. The last Swedish Crusade to Finland took place in 1293 against Karelians.