This treaty brought Lithuania under Swedish protection during the Second Northern War, foreshadowing the full Union of Kėdainiai two months later.
Key Facts
- Date signed
- 17 August 1655
- Context
- Second Northern War
- Lithuanian signatory
- Hetman Janusz Radziwiłł
- Superseded by
- Union of Kėdainiai, 20 October 1655
- Commonwealth dissolved?
- No — treaty explicitly preserved it
Location
Cause → Event → Consequence
Following the decisive Swedish victory at the Battle of Ujście, where the Poznań and Kalisz palatines surrendered, Lithuanian hetman Janusz Radziwiłł concluded that continued resistance was futile and that Polish support for Lithuania was insufficient to justify prolonging the conflict.
On 17 August 1655 in Kėdainiai, Lithuanian hetman Janusz Radziwiłł concluded an agreement placing Lithuania under Swedish protection. The treaty stipulated that the Polish–Lithuanian Commonwealth would not be dissolved and that Lithuanian forces would not engage Polish forces, while formally protesting the absence of Polish military support.
The treaty lasted only two months before being superseded on 20 October 1655 by the Union of Kėdainiai, which formally united the Grand Duchy of Lithuania with the Swedish Empire, marking a deeper rupture within the Polish–Lithuanian Commonwealth during the Second Northern War.
Political Outcome
Lithuania accepted Swedish protection while formally preserving the Polish–Lithuanian Commonwealth; superseded by the Union of Kėdainiai on 20 October 1655.
Lithuania part of the Polish–Lithuanian Commonwealth, engaged in the Second Northern War
Lithuania under Swedish protection, effectively separated from Polish military command