Keidana (Kėdainiai) Treaty
a treaty concluded in the city of Keidana (Kėdainiai) on Aug. 17, 1655, between the high Lithuanian feudal lords and the commanders of the Swedish troops; the document provided for the union of Lithuania with Sweden.
In the summer of 1655, Sweden started a war against the Rzeczpospolita (the Commonwealth of Poland and Lithuania) and seized the whole western part of Lithuania. A group of magnates headed by the supreme Lithuanian hetman Jonušas Radvila (Radziwiłł) agreed to recognize Swedish authority on the condition that the political role and landed estates of the Lithuanian feudal lords be preserved. The Keidana Treaty was not accepted by the population of Lithuania, nor was it confirmed by the Swedish king Charles X. However, the treaty helped the Swedes to occupy all of Lithuania, because the magnates did not oppose the Swedish troops.