Gulf of Finland Blockade

Germany starts Operation Barbarossa on the morning of 22 June 1941. Soon after this, on 10 July, the Karelian Army commanded by Field Marshall Mannerheim launches an attack on the Soviet Union.

In his radio broadcast on 26 June 1941, Finland’s President Ryti compares the Hanko military base to a pistol aimed at the heart of Finland.

The Finns call the leased area the Hanko Encirclement. The area does not, however, remain encircled; it stays open on the seaside, and the minefields do not prevent connecting traffic to the town.

On the eve of Operation Barbarossa, the Finns already start the blockade of the Soviet fleet in the Gulf of Finland in cooperation with the German troops that advance towards the southern coast of the Gulf of Finland.

On the first night of Operation Barbarossa, the Germans, assisted by Finns, lay almost a thousand mines at the entrance to the Gulf of Finland.

The mine and artillery blockade between the islands of Mäkiluoto and Naissaari works exactly as the Finns and Estonians have planned before the war. The blockade secures the sea transport of war materiel and foodstuffs from Germany to Finland. In spite of its huge power, the Soviet Baltic Fleet loses its significance right at the beginning of the war. It is forced to navigate through the narrow coastal passages off the Baltic coastline.

The mines cause significant losses to the Soviet Union.

Finland’s most powerful guns are located in Fort Mäkiluoto. The location allows Finns to fire across the narrow passage in the Gulf of Finland between Finland and Estonia. However, the guns need support from a fire control centre located on the southern coast of the Gulf. At the beginning of the Continuation War such a centre is built on the island of Naissaari. The centre is manned with Finns and connected to the Mäkiluoto fire control network through radio transmission and sea cables.