That leader also allied with George II of Transylvania in the Treaty of Radnot.
This conflict began with the contested election of a king who resigned from the cardinalship upon the death of his brother. During this conflict, Janusz Radziwiłł was the de facto ruler of one side, and gained the enmity of the nobility by signing the Union of Kėdainiai with the leader of the invading army. That leader also allied with George II of Transylvania in the Treaty of Radnot. This conflict was ended by the Treaty of Oliva, and the larger war prompted by this conflict was ended by the Treaty of Andrusovo. The common term for this conflict was coined by (*) Henryk Sienkiewicz in a novel that followed With Fire and Sword. For 10 points, name this late 17th century conflict which began with an invasion by Charles X Gustav and devastated the Polish-Lithuanian Commonwealth.
This conflict began with the contested election of a king who resigned from the cardinalship upon the death of his brother.
Swedish Deluge (or Second Northern War; prompt on "Northern War"; prompt on "Polish-Swedish War")