Soviet submarine S-363

Soviet submarine S-363 was a Soviet Navy of the Baltic Fleet, which became famous under the designation U 137 when it ran aground on October 27, 1981 on the south coast of Sweden, approximately 10 km from Karlskrona, one of the larger Swedish naval bases. The ensuing international incident is often referred to as "Whiskey on the rocks". U137 was the unofficial Swedish name for the vessel, as the Soviets considered names of most of their submarines to be classified at the time and did not disclose them.

Standoff
In October 1981, the Soviet submarine S-363 accidentally hit an underwater rock about 2 km from the main Swedish naval base at Karlskrona, surfacing within Swedish waters. The boat's presence coincided with a Swedish naval exercise, testing new equipment, in the area during the same days. Swedish naval forces reacted to the breach of neutrality by sending an unarmed naval officer aboard the boat to meet the captain and demand an explanation. The captain initially claimed that simultaneous failures of navigational equipment had caused the boat to get lost (despite the fact that the boat had already somehow navigated through a treacherous series of rocks, straits, and islands to get so close to the naval base). The Soviet navy would later issue a conflicting statement claiming that the boat had been forced into Swedish waters due to severe distress, although the boat had never sent a distress signal, but rather, attempted to escape.

The Soviet Navy sent a rescue task force to the site in Sweden, commanded by Vice-Admiral Aleksky Kalinin on board the destroyer Obraztsovy; the rest of the fleet was composed of a Kotlin-class destroyer, two Nanuchka-class corvettes and a Riga-class frigate. Sweden's centre-right government at the time was determined to safeguard Sweden's territorial integrity. As the Soviet recovery fleet appeared off the coast on the first day, a fixed coastal artillery battery locked onto the ships, indicating to the Soviets that there were active coastal batteries on the islands. The fleet did not turn immediately and as they came closer to the 12 mi territorial limit the battery was ordered to go into war mode on its targeting radar, turning it from a single frequency mode to a frequency-hopping mode. The Soviet fleet reacted almost immediately and all vessels except a heavy tugboat turned and stayed in international waters. Swedish torpedo boats confronted the tugboat, which left as well.

The Swedes determined to continue investigating the circumstances of the situation. The Soviet captain, after a guarantee of his immunity, was taken off the boat and interrogated in the presence of Soviet representatives. Additionally, Swedish naval officers examined the logbooks and instruments of the submarine. The Swedish Defense Research Agency also secretly measured for radioactive materials from outside the hull, using gamma ray spectroscopy from a specially configured Coast Guard boat. They detected something that was almost certainly Uranium-238 inside the submarine, localized to the port torpedo tube. Uranium-238 was routinely used as cladding in nuclear weapons and the Swedes suspected that the submarine was in fact nuclear armed. The yield of the probable weapon was estimated to be the same as the bomb dropped over Nagasaki in 1945. Although the presence of nuclear weapons on board the S-363 was never officially confirmed by the Soviet authorities, the vessel's political officer, Vasily Besedin, later confirmed that there were nuclear warheads on some of the torpedoes, and that the crew was ordered to destroy the boat, including these warheads, if Swedish forces tried to take control of the vessel.

As the Soviet captain was being interrogated, the weather turned bad and the Soviet submarine sent a distress call. In Swedish radar control centers, the storm interfered with the radar image. Soviet jamming could also have been a factor. As the Soviet submarine sent its distress call, two ships coming from the direction of the nearby Soviet armada were detected passing the 12 mi limit headed for Karlskrona.

This produced the most dangerous period of the crisis and is the time where the Swedish Prime Minister Thorbjörn Fälldin gave his order to "Hold the border" to the Supreme Commander of the Swedish Armed Forces. The coastal battery, now fully manned as well as the mobile coastal artillery guns and mine stations, went to "Action Stations". The Swedish Air Force scrambled strike aircraft armed with modern anti-ship missiles and reconnaissance aircraft knowing that the weather did not allow rescue helicopters to fly in the event of an engagement. After a tense 30 minutes, Swedish Fast Attack Craft met the ships and identified them as West German grain carriers.

The boat was stuck on the rock for nearly 10 days. Finally on November 5 it was hauled off the rocks by Swedish tugs and escorted to international waters where it was handed over to the Soviet fleet.

Interpretations
At the time, the incident was generally seen as a proof of widespread Soviet infiltration of the Swedish coastline.

In an interview in 2006, Vasily Besedin, the political officer on board, gave a different picture. The vessel had dual navigation systems, a well-trained crew and the captain Pyotr Gushchin was amongst the best. On board was staff officer Joseph Avrukevich who was trained in security techniques. Besedin claimed the incident was caused by an error in calculations by the navigation officer.

The area in which the Soviet submarine ran aground was at the time a restricted military zone where no foreign nationals were allowed. The exact location served as one of only two routes that could be used to move bigger ships from the naval base in Karlskrona to open water.

This incident is popularly known in the West as "Whisky on the rocks". In the Soviet Navy the submarine type came to be known as "Swedish Komsomolets", a pun on both the incident and the then widespread tendency to give the submarines Komsomol-themed names.