sovereigns in those provinces. After fighting along with the Swedish Army in 1656, most prominently at the Battle of Warsaw, Hohenzollern Frederick William I was willing to abandon his ally when the war had turned against them and signalled his willingness to change sides if Polish King John II Casimir Vasa would grant him similar privileges as previously Swedish King Charles X Gustav, conditions that were negotiated in Wehlau (Welawa, now Znamensk) and Bromberg (Bygost, Bydgoszcz). The Polish interest in an alliance with Brandenburg-Prussia was born out of the need to end the war against Sweden as soon as possible. On 3 November 1656, the Truce of Vilna had promised Alexis of Russia's election as a successor on the Polish throne at the next diet in return for halting his offensive in Poland–Lithuania and to fight Sweden instead. In the Grand Duchy of Lithuania, there was support for the treaty from the nobles, who hoped for positions with more privilege, but that was not true for the Kingdom of Poland, where the elites looked for ways to circumvent Alexis's succession. For a fast end to the war against Sweden to be able to avoid the implementation of the Truce of Vilna, the anti-Swedish alliance had to be extended. The newly won Russian ally was reluctant to support Poland against Sweden as long as no diet had confirmed the truce. A second ally, the Austrian Habsburgs, were won in the first and the second Vienna Treaties, but the Habsburg forces were to be maintained by Poland, the prize for the alliance was bound to rise while the war lasted. A third ally was Denmark-Norway, which joined the anti-Swedish coalition in June 1657 after it had been triggered by the second Treaty of Vienna. However, Denmark was not fighting on Polish soil, and although its involvement tied down Charles X Gustav's forces and a formal alliance with Poland was concluded in July, the Danish aimed to recover Scandinavian territories, which had been lost at the Second Treaty of Brömsebro (1645). The Habsburgs' interest in the treaty was to build up good relations with Frederick William I. As a prince-elector, he was a valuable ally if he supported their policy in the Holy Roman Empire. Thus, the Habsburgs were interested in Frederick William I changing sides and sent diplomat Franz Paul Freiherr von Lisola to mediate a respective settlement. Bromberg and Wehlau are