#Borders today takes us to the treaty that – more or less – defined the Scandinavian geography as we know it today: the Treaty of Roskilde (1658), which – almost – ended the Second Northern War. After the end of the 1618-1648 Thirty Years’ War, one of the worst pan-European conflicts in history, Sweden emerged as a superpower, and it could therefore focus on the war against the Polish–Lithuanian Commonwealth, of which Denmark-Norway was an ally.
The war ended in a devastating defeat for Denmark, which was forced to give up a third of its territory in order to save the rest. The country had to cede the land comprising Blekinge, Bornholm, Bohuslän (Båhuslen), Scania (Skåne) and Trøndelag; it also had to renounce any claim over Halland, a contested territory that had already been conceded to Sweden after the Treaty of Brömsebro (see our third #Borders post).
All the mentioned territories are still part of Sweden today, except for Trøndelag and Bornholm, that were returned to Denmark with the 1660 Treaty of Copenhagen, which posed a final end to the war by agreeing to less drastic measures (Trondelag is today part of Norway, Bornholm remains Danish). In any case, the Treaty of Roskilde was a landmark in Scandinavian history, and it defined the political #Borders that we know today.