During the Viking Age (800-1050) Swedish Vikings sought contact with Finns, aimed at establishing trade ties with the Arab world, through Russia.
Swedish influence in Finland grew, towards the close of the Viking Age, which saw Swedes converted to Christianity by the Roman Catholic Church. Many Finns were converted to the Roman Catholic faith during the mid 12thcentury, around the time of the Crusades.
Historical legend maintains that the crusade of 1157, led against the Finns by the Swedish King Eric IX, and an English monk, named Henry, an appointed archbishop. Henry was martyred in Finland, and became the country’s patron saint.
Russian forces sought control of Finland based on religious grounds. They who were of Eastern Orthodox Christianity attempted to convert the Finns to their religious order. Those of Eastern Karelia were converted, whilst those in the west remained Roman Catholic.
Around 1240, Rome approved two Crusades; Swedish Crusaders invaded Russia, and were brought to a stop on the banks of the Neva River by Prince Alexander of Novgorod. The Second Crusade led by the Teutonic Knights were defeated by Alexander Nevsky at Lake Peipus in 1242. The Swedes made a final attempt to take back Eastern Karelia from the Russians in 1293, but that was not to be. A Thirty Years War failed to dislodge the Russians from the region. The war ended in 1323 by Peace of Pahkinasaari, which established a border between Russia and Finland, which lasted nearly three hundred years.
Sweden consolidated its control over Finland, a process which led to the introduction of Swedish settlers along southern and western coastal areas of Finland. Most would remain in these coastal regions becoming members of a ruling class within Finland, and politically integrated into the Swedish realm.