the borders between denmark, sweden and norway came to the shape they have today in the middle of the seventeenth century: in the 1645 treaty of brömsebro, denmark–norway gave some territory to sweden: the norwegian provinces of jämtland, härjedalen and idre &amp; särna and the baltic sea islands of gotland and ösel (in estonia). the 1658 treaty of roskilde forced denmark–norway to give the danish provinces scania, blekinge, halland, bornholm, and the norwegian provinces of båhuslen and trøndelag to sweden. in 1660, the treaty of copenhagen forced sweden to give bornholm and trøndelag back to denmark–norway.