The naval battle of Salis (23/24 March 1609) was an important milestone in the 1600-1611 Polish-Swedish war, an example of the use of the element of surprise and innovation by the great Polish war strategist, Hetman Jan Karol Chodkiewicz.

The Lithuanian Hetman Jan Karol Chodkiewicz moved to the aid of Riga, threatened by the Swedes. Today’s capital of Latvia was then part of the Polish-Lithuanian state known as the Polish-Lithuanian Commonwealth. The two states – Poland and Lithuania – were officially united as a result of the Union of Lublin concluded on 1 July 1569.

During the expedition, the commander noticed a Swedish fleet stationed in the port of Salis (present-day Latvia), blockading Riga, consisting of 8 warships and 11 auxiliary vessels. The Swedes felt very confident as they were in complete control of the sea. Chodkiewicz saw in the dormant vigilance of the Swedes an opportunity to surprise and defeat the enemy. 

The Hetman sent two previously captured ships reinforced with an enlistment of Livonian sailors into battle. He bought five ( a probable number) merchant ships from Dutch and English owners. He armed them hastily and manned them with sailors. 

Surprisingly for the Swedish army, on the night of 23-24 March 1609, the Grand Hetman of Lithuania attacked. The Livonian sailors took advantage of the favourable winds and pushed floating vessels filled with flammable materials (branders) towards the enemy ships. This was probably the first time they were used in battle in the Baltic Sea. 

Surprised Swedes panicked. Two of their ships were burned. When fleeing, they came under fire from Polish-Lithuanian ships. The Swedish troops concentrated on escaping and did not even respond with artillery. 

Hetman Chodkiewicz, who turned out to be a great admiral, seized the port and food and weapons supplies. The victorious naval battle forced the Swedes to halt their attack on Riga.