The Swedish invasion of the Polish–Lithuanian Commonwealth, known as the Deluge (1655–1660), unfolded within the larger context of the Second Northern War. By this point, the Commonwealth had already been severely weakened by successive wars with Russia and the ongoing Khmelnytsky Uprising. Russian forces occupied most of the Grand Duchy of Lithuania, while Cossack forces controlled large portions of Ukraine. This fragmentation left the Commonwealth vulnerable to opportunistic attacks, especially from Sweden, which sought to exploit the Commonwealth’s internal instability.
The occupation of the Polish–Lithuanian Commonwealth (union state of the Crown of the Kingdom of Poland and Grand Duchy of Lithuania) during The Deluge and Chmielnicki's Uprising. © Halibutt
Invasion and Lithuanian Involvement
Sweden's King Charles X Gustav launched his invasion in 1655 with the intent of dominating the Baltic region. Lithuania’s weakened state led to divided loyalties among the nobility, with figures like Janusz Radziwiłł signing the controversial Union of Kėdainiai, aligning Lithuania with Sweden to counterbalance Russian advances. The defection of Lithuanian leaders like the Radziwiłłs, however, further fragmented the Commonwealth and inflamed tensions within the union between Poland and Lithuania.
Military Collapse and Guerrilla Resistance
Swedish forces rapidly captured major Commonwealth territories, including the cities of Kraków and Warsaw, encountering minimal resistance from the disorganized armies. Meanwhile, Lithuanian troops under Paweł Jan Sapieha resisted both Swedish and Russian forces, maintaining loyalty to John Casimir. With key Polish-Lithuanian leaders either defeated or in exile, much of the resistance came from local uprisings—peasants, townsfolk, and loyalist nobility—especially in areas like Greater Poland and the Lithuanian countryside. These irregular forces, inspired by guerrilla tactics, played a significant role in disrupting Swedish control.
Jasna Góra and the Turning Point
The defense of the Jasna Góra Monastery became a symbol of Polish resistance, galvanizing efforts against the invaders. In 1656, John Casimir returned from exile and rallied support for a national uprising. Lithuania, though weakened by losses, played a key role in guerrilla campaigns and helped block Swedish advances alongside Polish allies.
Political Shifts and Treaties
The war forced Sweden to alter its strategies, especially as Russia, which initially expanded into Lithuanian territories, grew wary of unchecked Swedish power. This shift led to a realignment: the Commonwealth reached an agreement with Russia to jointly oppose Sweden, though this treaty came at the cost of recognizing Russian territorial gains in the east. In 1657, Brandenburg-Prussia broke with Sweden, and by 1660, the Treaty of Oliva ended the war. However, the Commonwealth’s recovery was limited—Lithuania was left devastated, and Swedish forces had inflicted widespread destruction across the region.
Aftermath for Lithuania and the Commonwealth
The Deluge profoundly damaged Lithuania and the rest of the Commonwealth, marking a turning point in the region’s fortunes. Lithuania, already reeling from the Khmelnytsky Uprising and Russian incursions, emerged from the war economically devastated and politically weakened. The Commonwealth’s Baltic ambitions were curtailed, and Lithuania struggled to recover from the demographic and material losses. Moreover, the growing influence of Brandenburg-Prussia and Russia foreshadowed the decline of the Commonwealth’s power, setting the stage for future conflicts and the eventual partitions of Poland and Lithuania in the 18th century.