Russian forces were advancing into the unprotected…
March 1655 CE
Russian forces were advancing into the unprotected Commonwealth at the time of the accession of Charles X Gustav to the Swedish throne, and by focusing on the northeast these moves have drawn close to the Swedish sphere of interest at the Baltic coast.
Sweden, at this time an expansionist empire with an army designed to be maintained by the revenues of occupied territory, is conscious that a direct attack on her main adversary Russia could well result in a Dano-Polish-Russian alliance.
Also, Sweden is prevented from forming a Swedish-Polish alliance by the refusal of John II Casimir to drop his claims to the Swedish crown and the unwillingness of the Polish-Lithuanian nobility to make the territorial and political concessions an alliance with Sweden would eventually cost.
Final negotiations in Lübeck during February 1655 had ended without a result.
Thus, Sweden opts for a preemptive attack on the Polish-Lithuanian Commonwealth to occupy its yet available territories before the Russians.
The Riksdag that assembles at Stockholm in March 1655 duly considers the two great pressing national questions: war, and the restitution of the alienated crown lands.
A secret committee presided over by the King over three days decides the war question: Charles X easily persuades the delegates that a war against Poland appears necessary and might prove very advantageous; but the consideration of the question of the subsidies due to the crown for military purposes is postponed to the following Riksdag.