One second Swedish crusade (1238 or 1249) consolidated the new order in Häme. At the end of the XII E century, the Swedes had extended their power as far as Karelia; in 1293, they built there the castle of Vyborg (Viipuri in Finnish), assuming a territory on which the Russians of Novgorod intended to make recognize their rights. Intermittent hostilities followed. The peace treaty of Pähkinäsaari, signed in 1323, divided Karelia between Sweden and Russia, at the same time defining, for the first time, the Eastern border of Finland.  

One had hardly needed more than one century and half so that the country became integral part of the kingdom of Sweden. Swedish colonists were established on the littoral, in the south and the west. For the first time, the Finnish “tribes”, except for an important part of Caréliens, were joined together under the same authority. In 1362, Finland obtained the right to take part in the election of kings de Suède, as well as the other provinces of the kingdom.  

Until the end of the Middle Ages, Finland was subjected to a double authority: that, initially, of the Swedish crown represented by a high aristocracy of especially Scandinavian origin, but that also of the bishops of Turku (in Swedish, Åbo), cultivated men, trained abroad - in general at the University of Paris where two of them had even been “vice-chancellors”. The influence of these bishops was often dominating and it was to return to the one of them, Michel Agricola (1510-1557), to make Finnish, for the needs for the Church and in accordance with the principles of the Reform Lutheran, a literary language.  

At the same time, Gustave I er Vasa, which reigned on Sweden-Finland of 1523 to 1560, put an end to Danish supremacy on the kingdom, broke with Rome and encouraged the colonization of the areas of north and the east, which was to lead to later conflicts and a long war with Russia. Second half of the XVI E century, during which his/her sons and grandsons disputed the throne, was one period agitated both for the Swedes the Finns. In Finland, the disorders culminated, in 1596-1597, in the war of Maillotins, a general rising directed against the authority of Klaus Fleming, the effective Master of the country.  

During the XVII E century, the accession of Sweden to the statute of European great power was not without consequences for Finland. In 1609, the hostilities began again with Russia, but by the peace treaty of Stolbova, which it signed in 1617, Gustave-Adolphe, assembled on the throne in 1611, pushed back his Eastern border to include in his kingdom the Western part of the lake Ladoga as well as Ingrie. Victorious with the east, this large sovereign, intervened in the west in the Thirty Year old war. The Finnish dragons cut a frightening reputation there, but its participation in the conflict was expensive Finland, in resources and men.  

The time was also characterized by a reinforcement of administrative centralization, a fast rise to power of the nobility, the failure of the Counter-Reformation and the triumph of the Church Lutheran whose king became “the supreme bishop”. The administrative reorganization bound more closely than ever Finland to the remainder of the kingdom and weakens its identity. The nobility benefitted from the dominant position acquired in particular during the victorious wars to transfer to its benefit, by means of “donations”, a substantial share of the tax on land paid up to that point with the Crown. The evolution tended to impoverish the peasants and to weaken their position. In the last part of the XVII E century, it was however a redistribution of the grounds “alienated” in the past with noble which stopped in Finland the development of the feudal system.  

No one living of the kingdom being authorized to confess another faith only the Lutheranism, Caréliens orthodoxe, subjected to attempts at conversion forced in the territories conquered in the east, emigrated in mass inside Russia - in the area of Tver, where their descendants still live - and of the colonists Lutherans replaced them. The Church had a great merit however: it was given the responsability to learn how to read with all.

The reign of Charles XI was marked in Finland, in 1695-1696, by a very hard famine which, according to the estimates, cost the life a third of the population. Under Charles XII (1697 to 1718), the Swedes faced all their neighbors in the Great War of the North (1700 to 1721), at the conclusion which the kingdom lost not only its Eastern possessions, including Ingrie and the south-east of Finland, but also its position of great power. During the war, Russia had occupied Finland during eight years (1713-1721), devastating the country completely; the period remained known in Finland under the name of “Great Anger” (or “Great Enmity”: Iso Viha). During a new confrontation with Russia (1741-1743), the tsarina Elisabeth endeavoured to turn over the Finns against Sweden by proposing the creation of autonomous Finland under Russian protectorate. This project remained temporarily without continuation and Russia annexed a new portion of the Finnish territory.  

The sufferings endured during these two conflicts and the rise of the Russian power led the Finns to doubt the capacity of Sweden to ensure their protection. When a new war opposed the kingdom to Russia (1788-1790), this pessimism encouraged a group of officers, directed by Göran Magnus Sprengtporten (1740-1819), to foment a plot in order to create an autonomous State which would be put under the protection of Russia. This attempt, the “conspiracy of Anjala”, showed a failure; it did not represent of it less the appearance of a real identity feeling. This one found soon its expression in the work of a professor of the university of Turku, Henrik Gabriel Porthan, whose example encouraged the rising generation to study the past, the language and the culture of the Finnish people.