During the 11th and 12th centuries,
Sweden gradually became a unified Christian kingdom that later included what is today Finland. During the early Middle Ages, the Swedish state also expanded to control
Norrland and
Finland. Modern Sweden started out of the
Kalmar Union formed in 1397 and by the unification of the country by King
Gustav Vasa in the 16th century. Vasa fought for an independent Sweden and broke with the
papacy, establishing the
Lutheran Church in Sweden. In the 17th century Sweden expanded its territories to form the
Swedish empire. Most of these conquered territories had to be given up during the 18th century.