Edited map from the work Raunio, Ari, Sotatoimet – Suomen sotien 1939−45 kulku kartoin (Military Operations – The Course of Finnish Wars in 1939–45 with Maps), 3rd edition, Karttakeskus 2013.

The naval forces had to protect the maritime routes to the west

The main mission of the naval forces was to protect the maritime routes. The navy also had to participate in repelling landings and any hostilities against the coastline.

In the protection of the maritime routes, the main focus had to be on western connections. The navy particularly had to protect the routes on the Finnish Archipelago Sea and the Sea of Åland. The maritime traffic on the Gulf of Bothnia had to be protected by preventing the enemy’s warships from accessing the gulf.

On the Gulf of Finland, the naval forces had to prepare to repel any enemy attacks on the coast as well as possible landings. The Hanko Peninsula and its surroundings were considered to be the area most vulnerable to a landing.

The Åland Coast Guard District started escort operations on 7 October.

At the beginning of September, the Germans started conducting inspections on merchant ships on the Baltic Sea. These inspections also extended to the Gulf of Bothnia. On 7 October, Finland began to escort its own ships as well as those of neutral countries from the Åland Islands to the Swedish territorial waters. The escort operations were led by the Åland Coast Guard District. Its patrol boats provided the escort. Escort operations continued on the Sea of Åland after the start of the war, but they were reduced after mid-January due to ice.

The Germans also inspected several Finnish ships. According to the Germans, some of the inspected ships carried contraband of war as cargo. Any ships deemed as such were transported to German ports. Seventeen of the seized Finnish ships were released at the end of December, but six ships remained seized.

Icebreaker Squadron

The icebreakers were armed during the additional refresher training in October. The Icebreaker Squadron was formed under the Southwest Finland Naval Defence. It was tasked with maintaining transport operations during winter, supporting the escort service and participating in coastal defence.

The first armed vessels of the squadron were the icebreakers Jääkarhu and Tarmo. The armament took its time. The icebreaker Voima was added to the squadron on 30 November and the icebreaker Sampo on 2 December.

Soviet naval forces on the Baltic Sea

The Twice Red Banner Baltic Fleet had a great number of warships compared to the Finnish naval forces. Theoretically, the Twice Red Banner Baltic Fleet’s strength compared to Finland was enough to give the Soviet Union command of the sea on the Gulf of Finland and the northern Baltic Sea.

The great firepower of the Twice Red Banner Baltic Fleet was represented by its two ships of the line and two cruisers. The fleet had 15 destroyer-class vessels, 10 of which were new (G-class). Other vessels in the fleet included 52 submarines and several dozen motor torpedo boats. The Twice Red Banner Baltic Fleet was commanded by Captain 2nd Rank V. Tributs.

The Soviet Navy’s bases in the Baltic countries and the blockade of Finland

The Soviet Navy’s operations on the Gulf of Finland and the Baltic Sea were facilitated by the naval bases it obtained from Estonia and Latvia. Submarines, light surface vessels and other vessels were relocated there. They were used to blockade the coast of Finland.

On 7 December, the Soviet Union declared the coast of Finland to be blockaded. Neutral merchant ships had to exit the blockaded areas by 12 noon on 9 December. The blockaded area was expanded on 17 December to include some of the sea areas of the demilitarised zone of the Åland Islands. Submarines bore the main responsibility for the blockade. They were ordered to start a tonnage war at 12 midnight on 10 December.

Soviet submarines sank three vessels on 10 December

The submarine Shch-323 shelled and sank the Estonian steamer Kassari between Utö and Hiiumaa in the small hours of 10 December. The crew escaped on a lifeboat to Hiiumaa. Off the coast of Helsinki, the submarine Shch-322 sank the German steamer Reinbeck with torpedoes. The third sinking of the same day, that of the German steamer Bolheim, took place on the Gulf of Bothnia. The news of the sinking was not received until two days later, when the survivors arrived in Merikarvia on lifeboats.

The ice season that prevented ship traffic started in the second half of January. In the area south of Kvarken, the Finnish steamer Wilpas ran aground after the submarine Shch-311 opened fire on it. The submarine kept shelling the grounded ship until it became a wreck. The same submarine sank the Swedish steamer Fenris in Norrland’s waters on 1 January 1940.

Escort operations on the Bothnian Sea

Escort operations commenced on the Bothnian Sea on the Gulf of Bothnia in December. Convoys also travelled along the coast of Finland from the Rönnskär Archipelago off the coast of Vaasa via Kaskinen and Mäntyluoto to Lyökki, an island between Rauma and Uusikaupunki. The journey lasted less than a day. The convoys departed every other day in each direction. Another escort route travelled north of the Åland Islands from the island of Saggö to the Swedish territorial waters. This route could be operated in both directions on the same day.

The gunboats Uusimaa and Hämeenmaa participated in the escort operations on the Bothnian Sea from January onwards.

Aura II sank on 13 January 1940 while protecting a convoy on the Bothnian Sea as a result of its own depth charge exploding when being fired. It was attempting to bomb the Soviet submarine Shch-324. The accident killed 26 of the 44 crew members on board.

Soviet submarines left the Gulf of Bothnia on 19 January 1940

According to Finnish intelligence, the last Soviet submarine left the Gulf of Bothnia on 19 January 1940. After the start of the ice season, the Twice Red Banner Baltic Fleet bore the main responsibility for the blockade of the coast of Finland. In addition to launching aerial attacks, Soviet aircraft also dropped mines on the Finnish waterways.

Ice road of Kvarken

Thick ice hampered ship traffic. On the other hand, it made it possible to build an ice road between Sweden and Finland at Kvarken, leading from Vaasa to Umeå. The ice road, known as the Gräsbeck road, was in use from 17 February to 24 March 1940. The road made freight transport easier between Sweden and Finland.

The Coastal Fleet had significant air defence strength

The military operations of the Coastal Fleet’s most heavy-duty armoured ships during the Winter War primarily comprised air defence, first in the Åland Islands and the Turku Archipelago and later at the Port of Turku. The armoured ships had the most efficient air defence capability. The Soviet Air Force searched for them in the first stage of the war and launched aerial attacks on them after locating them. The Soviet Air Force launched a total of 53 attacks on armoured ships during the Winter War.

The collective deployment of the Coastal Fleet ended in January

It appears that the existence of the Coastal Fleet prevented Soviet surface vessels from attacking the Åland Islands and penetrating into the Gulf of Bothnia.

On 19 January 1940, the Coastal Fleet was ordered by the commander of the navy to relocate from the Åland Islands to the Turku Archipelago to protect the ship traffic to and from Turku. The armoured ships were relocated to Airisto. In practice, this marked the end of the collective deployment of the Coastal Fleet.

The operations of Finnish submarines yielded no results

Some of the Finnish submarines were in the Coastal Fleet, while others operated under the

commander of the navy. The small number of submarines was mainly used individually. One submarine travelled to Latvia’s territorial waters, off the coast of Liepāja. However, the submarines failed to sink any enemy vessels.

The Ladoga Naval Detachment participated in maritime transport

The Finnish Ladoga Naval Detachment was tasked with laying mines in the protected zones of the coast, fortifications and the archipelago’s waterways. In addition to patrolling the waters, the detachment also had to prepare for battle against the enemy’s light naval forces in the waters of the fortified islands together with the coastal forces. The detachment had to participate in transporting troops and supplies to the forts.

The detachment’s gunboats in military operations

The Ladoga Naval Detachment had five gunboats at its disposal. The detachment’s sixth gunboat ran aground and sank during the additional refresher training. The vessels were fitted with guns during the additional refresher training. Only the all-weather ship Aallokas and the tugboats Vulcan and Tarmo could be armed with 75 mm calibre guns. In compliance with the Treaty of Tartu, the other vessels were only equipped with 47 mm calibre guns, which were allowed on Lake Ladoga.

The enemy’s naval forces did not enter the detachment’s operating area. The detachment participated in supporting the battles of the IV Corps in the area between Impilahti and Pitkäranta (Pitkyaranta). The detachment’s gunboats shelled Pitkäranta and Koirinoja, among other places.

The gunboats participated in and protected transport. The most significant troop transport operations took place in December, when the detachment transported the 23rd Separate Battalion to the Valamo (Valaam) Island and from there to the fortified Mantsinsaari Island. The 4th Separate Bicycle Company was transported directly to Mantsinsaari from Lahdenpohja (Lakhdenpokhya).

The ships of the Ladoga Naval Detachment could not be transported to Finland after the end of the war

After the Winter War officially ended at 11am on 13 March, the troops of the Ladoga Naval Detachment began to withdraw behind the new border. The detachment was only able to bring the motorboats back to Finland and had to leave behind the rest of its ships, which it sunk. The naval detachment’s personnel relocated from Lahdenpohja to Savonlinna on skis.

Ari Raunio