Russia, the Grand Duchy of Lithuania would become a protectorate of Sweden, with a personal union joining both states. In addition, The Family would be given two sovereign principalities carved from its lands within the Grand Duchy, and the Lithuanian nobility would retain its liberties and privileges. Its main proponent, Janusz Radziwiłł, died only two months after it was signed, on 31 December at Tykocin Castle, which was then besieged by forces loyal to the King of Poland and the Grand Duke of Lithuania, John II Casimir. The castle was soon taken by Paweł Jan Sapieha, who immediately succeeded Janusz Radziwiłł to the office of Grand Hetman of Lithuania. The tide of the war soon turned and a popular uprising in Poland broke the power of the Swedish army. The Swedish occupation of Lithuania sparked a similar uprising in Lithuania. The Swedish defeat and the eventual retreat from the territories of the Commonwealth abruptly ended the plans of Janusz's cousin Bogusław, who lost his army in the Battle of Prostki and died in exile in Königsberg on 31 December 1669. With the passing of both cousins, the Radziwiłł family fortunes waned. Bogusław became commonly known as Gnida ("Louse") by his fellow nobles, and Janusz was called Zdrajca ("Traitor"). Their treason against the Commonwealth largely overshadowed the deeds of the next generation's numerous other family members, including Michał Kazimierz Radziwiłł (1625–1680), who served faithfully against the Swedes. Assessment Although seen as an act of treason by contemporaries, modern views on the Swedish–Lithuanian accord differ. Some argue that the arrangement with the Swedes was made by Janusz Radziwiłł not out of greed and the political ambition, but rather out of Realpolitik. According to another theory, Janusz Radziwiłł was merely attempting to secure a strong ally against Russia. The Grand Duchy of Lithuania lacked the resources to fight a war on two fronts, and the Polish Crown, which now had its own serious problems and could supply only trifling amounts of money and military forces. However, some Lithuanian intellectuals during the National Revival, including Maironis, praised the Lithuanian nobility for trying to secede from Poland and secure the sovereignty of Lithuania. See also Polish–Swedish union Sources References Bibliography Second Northern War 1655 in Lithuania 1655 in the Polish–Lithuanian Commonwealth 1655 treaties Kedainiai 1655 in Sweden Lithuania–Sweden relations Personal unions