The great struggle begun by the Cossacks, and, after the victory at Korsun, continued by them and the Russian population of the Commonwealth, is described in With Fire and Sword, from the ambush on the Omelnik1 to the battle of Berestechko. In The Deluge the Swedish invasion is the argument, and a mere reference is made to the war in which Moscow and the Ukraine are on one side and the Commonwealth on the other. In Pan Michael, the present volume and closing work of the trilogy, the invader is the Turk, whose forces, though victorious at Kamenyets, are defeated at Hotin.