The Peace of Westphalia considerably strengthened Sweden's position in Scandinavia and the Baltic. To the earlier conquests in the east—Ingria, Estonia and Livonia—were added western Pomerania, Bremen, Verden and Wismar in the Empire; the total population amounted to about 2,500,000 people, half of whom were Swedish. The peace did not, however, solve Sweden's problems at home and abroad, but created fresh problems. The new German provinces made Sweden a member of the Empire and she became more deeply involved in the intrigues and negotiations between the princes and the Emperor. Moreover, the new provinces were coveted by others. Brandenburg remained discontented because she failed to gain western Pomerania. Denmark and the Lüneburg princes wanted Bremen and Verden. In the east the fear persisted that Russia—after the ‘Time of Troubles’—would renew her attempts to break through to the Baltic.

Furthermore, Swedish successes in the Thirty Years War had not terminated the struggle for hegemony in the north between Sweden and Denmark, which dated from the fourteenth century. By the Peace of Brömsebro (1645) Denmark ceded to Sweden freedom from customs dues in the Sound as well as the Baltic islands of Gotland and Ösel, Jämtland, Härjedalen and Halland (the latter for thirty years). The gains of 1648 also meant that Sweden could attack Denmark from the south; but even so Denmark still constituted the greatest threat to Sweden's position. Denmark was eager to reconquer the provinces lost in 1645 and—since the struggle was fundamentally one over hegemony in the north—she necessarily considered it a fight for existence. Thus the Scandinavian countries, during the whole period to the outbreak of the Great Northern War in 1700, attempted to isolate each other by concluding alliances with each other's enemies among the European powers.