Academics debate whether this crusade actually took place. No archaeological data gives any support for it, and the earliest written sources are from much later. No surviving written source describes Finland under Swedish rule before the end of the 1240s. Furthermore, the diocese and the bishop of Finland are not listed among their Swedish counterparts before the 1250s. Also, the Christianisation of south-western Finland is known to have already started in the 10th century, and in the 12th century, the area was probably almost entirely Christian.[2]
The Swedish bishop who was normally involved in the eastern campaigns was the Bishop of Linköping, not the Bishop of Uppsala.[citation needed]
The mid-12th century was a very violent time in the northern Baltic Sea, with Finnish tribes such as the Tavastians and Karelians as well as Swedes in frequent conflicts with Novgorod and with one another.[4] The First Novgorod Chronicle relates that in 1142 a Swedish "prince" and bishop, accompanied by a fleet of 60 ships, plundered just three Novgorodian merchant vessels somewhere "on the other side of the sea", obviously after something more important.[5]
Almost every year of the 1150s has been suggested as the year that the crusade possibly took place. The most widely-supported years have been 1150, 1155, 1157 and 1158. Other candidates have been 1153, 1154 and 1156.[6]
At the time, leading the leiðangr was the responsibility of the jarl. That gave rise to a theory that Eric had conducted the expedition before he became king or pretender to the throne.[citation needed] Legends give no year for the expedition, but all attempts to date it to an exact year in the 1150s have been much later speculations. All that is known about King Eric and Bishop Henry is that they most probably held important positions in Sweden at some time during the mid-12th century.[citation needed]
Heikkilä, Tuomas (2006). Pyhän Henrikin Legenda. Helsinki: Suomalaisen kirjallisuuden seuran toimituksia 1039. pp. 138–139.
Georg Haggren, Petri Halinen, Mika Lavento, Sami Raninen ja Anna Wessman (2015). Muinaisuutemme jäljet. Gaudeamus. p. 343.{{cite book}}
: CS1 maint: multiple names: authors list (link) Heikkilä, Tuomas (2006). Pyhän Henrikin legenda. Helsinki: Suomalaisen kirjallisuuden seuran toimituksia 1039 (2.painos). pp. 55–56.