S2 (ex-Prozorlivy and ex-Gagara in Russian service) was a Finnish Sokol-class torpedo boat that had been seized from the Russians after the Finnish Civil War 1918. She sank during a fierce storm on 4 October 1925, taking with her the whole crew of 53.
Background
Between 1900 and 1908, the Russians built 25 Sokol class torpedo boats for the Russian Baltic Fleet. "Sokol" (Сокол) is Russian for Falcon). The fourth ship of the class, Gagara (Гагара, Russian for Loon), was built at the Neva shipyard in Saint Petersburg and carried the construction number 102.
On 9 March 1902 the ship was renamed Prozorlivy (Прозорливый, Russian for sharp or awake). She was used as a trawler in 1911, but when World War I ignited she was taken into service as a minesweeper and was based in a Finnish port.
The war was going badly for the Russians and the Russian Navy revolted. The revolts soon spread out in the nation and Finland managed to secure its independence from Russia in the turmoil. However, tensions were still running high and soon after the declaration of independence the Finnish Civil War erupted. The socialists (reds) and the non-socialists (whites) clashed. Elements of the Russian Baltic fleet were still moored in Finnish harbours and the Russian sailors were sympathetic with the socialist side. However, the Finnish reds faced tough pressure from the whites, who had better military leadership. A German force that landed in southern Finland – in the back of the reds – finally broke the reds''' fighting spirit.
The Russian fleet in Helsinki panicked when the Germans marched against Helsinki. They managed to secure a deal with the Germans, which allowed them to withdraw to Russia. However, only the largest ships managed to return to Russia, due to the harsh ice conditions of the Gulf of Finland. Numerous vessels were left behind to be seized by the whites and the German troops. On April 13, Prozorlivy was conquered by the whites and she was transferred to the Finnish navy, along with her five sister ships (Ryany (later S1), Poslishny (S3), Rezvy (S4), Podvizhny (S5) and No 212 (S6)).Prozorlivy served over seven years in the Finnish navy. During her first years, she supported British operations against the Bolshevik navy. In accordance with the Treaty of Tartu of 1920, three of the Sokol class ships were returned to the Soviet Union in 1922. It was also planned that Prozorlivy would have been handed over, but the ageing ship was sold to Finland, where she was included in the Finnish navy. Prozorlivy was renamed S2 in 1922 and she continued to serve the fleet until 4 October 1925, when she was lost at sea with all hands. The loss of S2 is the worst peacetime accident in the Finnish navy and it shocked both the navy and the country. The disaster was a major catalyst for a large renewal program of the Finnish fleet.
The last journey of the torpedo boat S2
One of the Finnish Navy's annual traditions was a naval visit to the Finnish coastal towns along the Gulf of Bothnia, the trip doubling as a training exercise for conscript sailors. In 1925, the gunboats Klas Horn and Hämeenmaa, as well as the torpedo boats S1 and S2, embarked on one such journey. The plan was to visit all the coastal cities up to Tornio and the group began the journey from Uusikaupunki to Vaasa on 3 October 1925. They traveled in line formation with one kabellängd () internal distance and at a speed of . S2 was positioned furthest back in the formation.
Initially everything went as planned, but as the journey progressed, the wind started to pick up and later developed into a fierce storm, which created difficulties for the ships. The crews had to increase the internal distance between the ships, and they were also forced to reduce speed.
The storm finally dispersed the formation when they reached the Pori parallel. Klas Horn, which was the lead ship of the formation, turned against the wind and headed towards the Swedish coast, followed by Hämeenmaa. The torpedo boats tried to follow the bigger vessels but were lagging behind due to the high waves. In the middle of the night, the wind speed reached hurricane force 48–55 m/s (), 12 on the Beaufort scale.