[2][1][5][6] The signatories were the Habsburg Holy Roman Emperor Leopold I, Elector Frederick William I of Brandenburg and King John II Casimir Vasa of Poland.

Even then, so many hostile words were written in the documents being exchanged by the two parties that the head negotiator, French ambassador Antoine de Lumbres [fr], found himself having to expurgate long sections which otherwise would have caused offense.

A Polish–Lithuanian contingent headed by the archbishop of Gniezno wanted the war to continue in order to expel the exhausted Swedish forces in Livonia.

Even Frederick William, Elector of Brandenburg offered assistance to Poland–Lithuania to continue the war, with the hope of conquering Swedish Pomerania.

The Austrian and Brandenburgian intrusion into Swedish Pomerania was considered a breach of the Peace of Westphalia, which France was under the obligation to prosecute.

France therefore threatened to contribute an army of 30,000 soldiers to the Swedish cause unless a treaty between Sweden and Brandenburg was concluded before February 1660.

[11] The treaty had John II Casimir renounce his claims to the Swedish crown, which his father Sigismund III Vasa had lost in 1599.