During the 13th century, Finland gradually came under Swedish rule through a series of crusades and military campaigns. The area of Finland was divided among various Finnic tribes and was also subject to influence and raids from Novgorod. Sweden established control over western Finland in the mid-13th century and the northern border between Catholic and Orthodox areas was set at the eastern border of Finland with the Treaty of Nöteborg in 1323. Finland was then integrated into the Kingdom of Sweden and the medieval European system, with the bishopric established in Turku becoming an influential religious and cultural center.