Ruotsinsalmi was a minelayer

Minelayer

Minelaying is the act of deploying explosive mines. Historically this has been carried out by ships, submarines and aircraft. Additionally, since World War I the term minelayer refers specifically to a naval ship used for deploying naval mines...

 of the Finnish Navy

Finnish Navy

The Finnish Navy is one of the branches of the Finnish Defence Forces. The Navy employs 2,300 people and about 4,300 conscripts are trained each year. Finnish Navy vessels are given the ship prefix "FNS" simply short for "Finnish Navy Ship"...

 and the namesake of her class

Ruotsinsalmi class minelayer

The Ruotsinsalmi class minelayers were a two-strong class of minelayers in the Finnish Navy.Both ships were launched in 1940 and named after famous 18th century sea battles between Sweden and Russia.- New minelayers for the navy :...

. Ruotsinsalmi was commissioned in 1940 and remained in service until 1975. The vessel was named after the battle of Ruotsinsalmi, which was fought between Sweden

Sweden

Sweden , officially the Kingdom of Sweden , is a Nordic country on the Scandinavian Peninsula in Northern Europe. Sweden borders with Norway and Finland and is connected to Denmark by a bridge-tunnel across the Öresund....

 and Russia

Russia

Russia or , officially known as both Russia and the Russian Federation , is a country in northern Eurasia. It is a federal semi-presidential republic, comprising 83 federal subjects...

 in 1790.

New minelayers for the navy

Funding for two new minelayers had been secured as early as in 1937, but instead the money was used to refurbish the garrison at Mäkiluoto

Mäkiluoto

Mäkiluoto is a Finnish island in the Gulf of Finland, just to the south of Porkkala peninsula. It is part of Kirkkonummi municipality. The whole island is an unmanned military installation and access for civilians is heavily restricted. A number of coastal artillery guns are emplaced...

.

Ruotsinsalmi and her sister vessel, Riilahti

Finnish minelayer Riilahti

Riilahti was a Ruotsinsalmi class minelayer of the Finnish Navy. Riilahti was commissioned in 1940 and sunk in 1943. The vessel was named after the battle of Riilahti, which was fought between Sweden and Russia in 1714.- New minelayers for the navy :...

, were intended as escort minesweepers

Minesweeper (ship)

A minesweeper is a small naval warship designed to counter the threat posed by naval mines. Minesweepers generally detect then neutralize mines in advance of other naval operations.-History:...

 for the Finnish navy's coastal defence ships Ilmarinen and Väinämöinen, and they were therefore designed with a draft of only 1.5 m. Ruotsinsalmi was armed with one 75 mm gun, one Bofors 40 mm gun

Bofors 40 mm gun

The Bofors 40 mm gun is an anti-aircraft autocannon designed by the Swedish defence firm of Bofors Defence...

s and two Madsen 20 mm anti-aircraft cannons. The vessel had three mine dropping rails, and could carry about 100 mines. The ship could also hunt submarines, and was equipped with sonar

Sonar

Sonar is a technique that uses sound propagation to navigate, communicate with or detect other vessels...

, depth charge

Depth charge

A depth charge is an anti-submarine warfare weapon intended to destroy or cripple a target submarine by the shock of exploding near it. Most use explosives and a fuze set to go off at a preselected depth in the ocean. Depth charges can be dropped by either surface ships, patrol aircraft, or from...

 throwers and rails. The vessel was also strong enough to be able to tow mine sweeping equipment. It was equipped with smoke generators so it could protect itself and other near-by vessels from the enemy.

Ruotsinsalmi during the Continuation War

Ruotsinsalmi and Riilahti began mining the Gulf of Finland

Gulf of Finland

The Gulf of Finland is the easternmost arm of the Baltic Sea. It extends between Finland and Estonia all the way to Saint Petersburg in Russia, where the river Neva drains into it. Other major cities around the gulf include Helsinki and Tallinn...

 on June 26, 1941, immediately after the outbreak of the Continuation War

Continuation War

The Continuation War was the second of two wars fought between Finland and the Soviet Union during World War II.At the time of the war, the Finnish side used the name to make clear its perceived relationship to the preceding Winter War...

.

Ruotsinsalmi was Finland's most active minelayer during the Second World War, laying a total of 3,967 sea mines and 541 sweeping obstacles. She was forced to lay mines against the Germans after the end of the hostilities with the Soviet Union.

She participated in the sinking of two Soviet submarines, ShCh 317

Shchuka class submarine

The Shchuka class submarines , also referred to as Shch or SC class submarines were a medium-sized class of Soviet submarines, built in large numbers and used during World War II...

 on 15 July 1942 (along with VMV 16) and ShCh 408

Shchuka class submarine

The Shchuka class submarines , also referred to as Shch or SC class submarines were a medium-sized class of Soviet submarines, built in large numbers and used during World War II...

 on 25 May 1943 (along with VMV 6).

After the war

Ruotsinsalmi had proven to be a sound design and well suited for its task. However, it continued to serve a number of different missions after the war. It ended its career as a diving support vessel (1973–1975). She was mothballed in Upinniemi, and there were plans to make her into a museum, but she was scrapped at the beginning of the 1990s, after the owners had failed to gather enough funds.