In the spring of 1790 King Gustav III of Sweden personally led a force of 4,000 men across the Kymi River in Finland at the then Swedish-Russian border.

The Swedes retreated in an orderly fashion and were soon reinforced when General Vilhelm Mauritz Pauli arrived with 1,200 men.

Meanwhile, the Russian force halted and positioned itself at the Keltis barracks, originally built as a Swedish guardpost, where it also received some reinforcements.

With his 2,000-man force General Pauli felt confident enough to launch a counterattack against the Russians and marched in the evening of May 19 against Keltis barracks.

During the night of May 19–20 the Swedes attacked and after a short but bloody battle the surprised and shaken Russians retreated.