For the 1789 battle of Svensksund, see first Battle of Svensksund. The Battle of Svensksund (Finnish: Ruotsinsalmi, Russian: Rochensalm) was a naval battle fought in the Gulf of Finland outside the present day city of Kotka on 9 and 10 July 1790. The Swedish naval forces dealt the Russian fleet a devastating defeat that resulted in an end to the Russo-Swedish War of 1788–90. The battle is the biggest Swedish naval victory and the largest naval battle ever in the Baltic Sea.