An ongoing Danish mediation of this conflict became void with the intervention of Sigismund II Augustus, king of Poland and Grand Duke of Lithuania and by the terms of Cracow protector of Wilhelm's brother, Albert.[5] He demanded that Wilhelm and Christopher be released and the Livonian Confederation accept his protection.[5] When he declared war[6] and raised an army to underline his demands,[5] which left for Livonia in July 1557,[7] the Livonians gave in and signed three respective treaties[8] on 14 September[9] in the encampment of Sigismund II Augustus' army near Pozvol (Pasvalys, Podzwol, Pozwoł).[10]
All three treaties concerned the relation between the Livonian estates and Sigismund.[11] The first two treaties were the result of a mediation by envoys from the Holy Roman Empire, and were drafted on 5 September.[6] Wilhelm was restored to his former position as archbishop, with his liberty and all former rights confirmed.[7] Livonia restored its relation to Lithuania, and both realms concluded a defense-offense pact.[8] The new grand master, Wilhelm von Fürstenberg, signed the alliance for the order[7] and also ratified the other two treaties on 14 September along with other members of the order.[11]
The tsar reacted to Pozvol by invading Livonia before the alliance would result in an actual mobilization of forces, starting the Livonian War (1558–1583).[1] As a result, Reval (Tallinn) turned to Sweden for protection, Ösel (Saaremaa) was occupied by Denmark-Norway, and the order's grand master Gotthard von Kettler secularized what was left of the Russian-occupied order state, formally subordinated it to Sigismund II Augustus, and established himself as duke of Courland.[3]
Kiaupa, Zigmantas (2005). The history of Lithuania (2 ed.). Baltos lankos. ISBN9955-584-87-4.
Lubieniecki, Stanisław (1995). Williams, George Huntston (ed.). History of the Polish Reformation. Harvard theological studies. Vol. 37. Fortress Press. ISBN0-8006-7085-X.
Macinnes, Allan I.; Riis, Thomas; Pedersen, Frederik, eds. (2000). Ships, guns, and Bibles in the North Sea and Baltic States, c. 1350-c. 1700. Northern European Historical Research Network Proceedings. Vol. 1. Tuckwell Press. ISBN1-86232-167-1.
Reddaway, William Fiddian (1978). The Cambridge history of Poland. Vol. 2. Octagon. ISBN0-374-91250-5.