- The Danish fleet under command of Søren Norby reach the besieged Stockholm.
- Gustav Vasa makes a treaty with Hanseatic Lübeck and establishes the Swedish fleet.
- Lübeck declare war against Denmark.
- Lübeck and Danzig form an alliance with Frederick I of Denmark against Christian II of Denmark.
- With the assistance of the fleet provided by their Hanseatic allies, the Swedes conquer all the strongholds in Sweden-Finland excepts for Stockholm, Kalmar and Älvsborg.
- The Swedish fleet rebuff another rescue expedition of Sören Norby to Stockholm.