Charles X Gustav of Sweden
When the Second Northern War broke out in 1654, Charles X Gustav of Sweden offered an alliance to Frederick William I, the "Great Elector" of Brandenburg and duke of Prussia. As the price for this alliance would have been the surrender of the Prussian ports of Pillau (now Baltiysk) and Memel (now Klaipėda) to Sweden, Frederick William I refused and instead signed a defensive alliance with the Dutch Republic in 1655.