Case study – submerged contacts in Swedish waters in the 1980s

A similar problem confronted Sweden, as well as other Scandinavian nations, during the 1980s in respect of submerged contacts in its territorial sea and internal waters. This was a serious threat to its sovereignty over those waters but did not pose an immediate thr eat to life. The nature of submarines being difficult to identify or communicate with when submerged poses quite a different problem to dealing with surface vessels. Submarines that are submerged in the territorial sea, without consent of the coastal state, are acting contrary to the requirements of article 20:

In the territorial sea, submarines and other underwater vehicles are required to navigate on the surface and to show their flag.

Frornan concisely described the Whiskey on the Rocks incident in 1984, referring to contemporaneous news reporting, as follows:

On the night of October 27, 1981, a Soviet ‘whiskey’ class submarine carrying a crew of 56 ran aground inside a restricted security zone nine miles southeast of the Karlskrona Naval Base, deep within Swedish territorial waters. Following an 11-day drama, which included lodging two diplomatic protests, sighting another submarine’s periscope and turning back a Soviet salvage vessel both inside Swedish territorial waters, and discovering uranium 238 emanating from the submarine’s hull, the Swedish government concluded ‘that the submarine had intentionally violated Swedish territory to gather intelligence’. Swedish Prime Minister Thorbjom Falldin initially called the episode ‘the most grave intrusion into Swedish territory since World War 1Г. He later termed the violation ‘all the more remarkable since in all probability the submarine has carried nuclear weapons into Swedish territory’. Its investigation closed, the Swedish Navy on November 6th escorted the submarine to the 12-mile limit, where it joined a flotilla of 20 Soviet warships waiting just outside.[1]

The Whiskey on the Rocks incident followed concerns about occasional Soviet submarine incursions into Swedish waters dating back to the 1930s but actually came at the begiiuiing of a period of heightened tension between Sweden and the Soviet Union which lasted from 1980 until at least 1990.4S This reportedly involved numerous incursions every year during the 1980s by Soviet submarines and divers, as well as operations ashore in Sweden launched from the sea as well as by other means. Swedish naval units actively pursued underwater contacts, using depth charges, toipedos, limpet mines and fixed minefields. Patrols ashore intercepted combat swimmers entering or leaving the water. Although much of the naval activity occurred after the Whiskey on the Rocks incident, it is important to place the incident within this context as it casts a different light on the actual character of the incident itself in retrospect. It also underlines its importance as an indicator of what was to come.

McCormick, in a 1990 Rand report for the US Ah Force on submarine incursions into Swedish waters throughout the 1980s, identified a number of aspects of the incident which are significant from a legal perspective as follows:

1 The Swedes protested formally to the Soviets that the grounding was a flagrant violation of Sweden’s sovereignty.

  • 2 The Soviets replied that the incident was the result of an innocent navigational error and strongly rejected Sweden’s demands that it not occur again, as it was impossible to deny the possibility of future accidents at sea.54
  • 3 The Soviet Union continued to assert the sovereign immunity of U137 and demanded that it be allowed to refloat the vessel and recover it. To this end it dispatched a surface force comprising three destroyers, a frigate, two missile boats, a submarine salvage vessel, two electronic warfare vessels and an oiler, which waited outside Swedish territorial waters.55
  • 4 Sweden replied that it required the Soviet Union to meet four conditions for the return of the submarine:
  • 1 The Royal Swedish Navy refloat the submarine;
  • 2 The Soviet Union bear the cost of the salvage;
  • 3 The Soviet Union apologise formally, and
  • 4 That the captain of U137 submit to Swedish questioning.56
  • 5 The Soviet Union agreed reluctantly to these demands, after which Swedish investigators boarded the vessel. Ten days after it grounded, U137 proceeded to sea on the surface and under tow.57

The grounding of U137 raises at least two issues which warrant further consideration. The first is the extent to which U137, and, separately, its crew, enjoyed sovereign immunity from law enforcement by Sweden. The second issue is the extent to which Sweden could use force either before or after the U137 incident against unidentified submarine contacts in Swedish waters.

Sovereign immunity of warships and crew, even if in violation of coastal state laws or security?

If there was no basis to claim force majeure or distress, the presence of U137 in Sweden’s internal waters was a serious breach of Sweden’s sovereignty. If this were the case, did it have any implications for the sovereign immunity of U137 and its crew? It appears that Sweden respected the sovereign immunity of U137 at all tunes, in that Swedish authorities did not board it until it had reached an agreement with the Soviet Union.58 This may have been a result of pragmatism on both sides. Sweden may not













have wished to provoke its large and powerfill neighbour. The Soviet Union may have wished to recover its submarine as soon as possible with minimal further incident. Similarly, Swedish authorities did not question the Soviet captain, Captain Second Rank (Lieutenant Commander) Gushchin, until after reaching agreement to do so with the Soviet Union.[2] Even if practical concerns determined the agreement between each state, it is still the case that, despite the apparent serious breach of Sweden's sovereignty, Sweden respected the sovereign immunity of U137 as a Soviet warship. Even if Sweden soon after took the view that it could attack submerged contacts in its waters, as discussed subsequently, such breaches of its sovereignty did not waive the Soviet Union’s sovereign immunity in respect of U137. This would suggest that the ‘Whiskey on the Rocks’ incident actually reinforced the principle of sovereign immunity of warships in situations other than aimed conflict, regardless of a whether a warship has breached the sovereignty of the coastal state. It would appear then, on this view, that a coastal state can force a vessel out of its waters but cannot board the vessel or question its crew without the consent of the flag state.

Use of force against submerged contacts

The Whiskey on the Rocks incident is perhaps more significant for what it led to in terms of Sweden’s use of force against submerged contacts in its waters. Whilst there was no use of force against U137, Sweden relied upon its apparent violation of Swedish sovereignty to justify subsequent actions. Notably, among others, the Harsfjarden incident lasted from 1 October to 1 November 1982 and involved the Royal Swedish Navy conducting antisubmarine warfare operations against multiple contacts in the vicinity of its largest naval base. There were also other frequent, similar incidents throughout the 1980s. The incursions were said to involve submarines, mini-submarines, combat swimmers and even a tracked submersible capable of travelling along the sea bed.[3] The apparent ptupose of these incursions was to test Swedish coastal defences both ashore and at sea and included interfering with minefields. The Swedes took the view that they could use force to compel a submerged contact to surface or in order to drive it out of Swedish waters. Swedish naval units were not to seek lethal destruction of submerged contacts (except possibly in then own self-defence). To this end, Swedish naval units deployed torpedos with reduced-charge warheads designed to damage only rudder and screws. They also deployed limpet mines, known as the Malin, which would attach to a hull and give off a locating signal, as well as a shaped charge, known as an Elma, which would also attach to a hull but cause an explosion large enough only to flood some compartments.

The Swedes did not, apparently, succeed in driving any submarines to the surface, but it is not known the extent to which they damaged or drove any out. The interesting legal point is the apparent lack of protest at any of this use of force. The Soviet Union, unsurprisingly, did not accept responsibility for any of the incursions into Swedish waters and presumably did not protest the use of force for this reason. The situation may have been different if Sweden had caused the loss of a submarine, a nuclear accident or significant loss of life. Even so, arguably, other states seem to have acquiesced in Sweden’s practice of forcibly responding to unknown submerged contacts. This would suggest that customary international law permits the use of force in defence of a coastal state’s sovereignty over its internal or territorial waters. This would either be to drive such contacts to the surface or out of a coastal state’s waters but not for the ptupose of lethal destruction, particularly noting the nuclear risk. Arguably this would meet the proportionality requirements of self-defence m international law as the threat from submerged contacts in coastal state waters is not necessarily lethal. If the threat were lethal, then the use of lethal force in defence against such contacts would arguably be less problematic. Lethal force may only be acceptable where the threat is lethal, whereas submerged intruders that do not pose a lethal threat may only be ejected with non-lethal, even if very forceful, means.


It is possible to apply the cases and the experience of Sweden to the law of the sea to derive some clear rules on the use of force and the presence of warships in the territorial sea and internal waters. There is very little that a warship can do in the territorial sea other than navigate continuously and expeditiously through in innocent passage. It may use force, however, to defend itself should it be threatened. Given that a state may close a territorial sea, it is not open to warships to assert passage, as in the Corfu Channel Case which involved an international strait. Warships may not clear obstructions nor escort other vessels.

For the coastal state, it may deny passage to warships where their passage is not innocent. If asked to leave and they do not do so, where there is a threat to the coastal state’s sovereignty, it is possible to use force against warships to the extent necessary to eject them from the territorial sea. The coastal state cannot infr inge the sovereign immunity of a warship by boarding or apprehension, however. There can be no use of lethal force except in response to a lethal act. Lethal force can include dangerous manoeuvering which poses a serious risk to life. This does not prevent the use of warning shots and even direct fire in cases where other measures have failed and there is little threat to life in doing so.

submerged passage may in fact be innocent, due to factors such as weather, but that submerged passage could also amotint to an aimed intrusion on the coastal state’s sovereignty. He accepts that some force may be used, patiently, to force a vessel to the surface, but that attacking a submerged contact directly could still give rise to a light of self-defence on the part of the submerged contact. O’Connell states that any forceful response to the submerged contact must be proportionate to the military threat prevailing at the time. This appears to be the most persuasive view of the law still. O’Connell and Shearer restate these views in essentially similar terms, with an emphasis on the point that it is a submarine's behaviour that renders its passage non-innocent, rather than the mere fact of it being submerged, in DP. O’Connell (edited by I.A. Shearer) The International Law of the Sea: Volume 1 (Clarendon, Oxford, 1982), 294-297. Yoram Dinstein has no reservations in regard to the use of force against submarines in such cases, citing state practice, but is more equivocal with regard to surface warships in Wai; Aggression and Self-Defence (6th ed, Cambridge, 2017) 214-215; the German and US Commander’s Handbooks are notably silent on this question.

As to internal waters, a warship still enjoys sovereign immunity and may still defend itself. It is really for the port or coastal state, however, to provide security for visiting warships, so the use of force should be limited to within the warship itself. This should only occur where the port or coastal state is unwilling or unable to protect the warship. Self-defence of a warship in internal waters may amount to using no more force than is necessary to enable the warship to leave the port or harbour if it is able to do so.

  • [1] David Froman, ‘Uncharted Waters: Non-rnnocent Passage of Warships in the Territorial Sea’ (1984) 21 San Diego Law Review 625, 626-627, and also the Norwegian experience 684-688; on the Danish experience, see Dieter Fleck, ‘Rules of Engagement for Maritime Forces and the Limitation of the Use of Force Under the UN Charter’ (1988) 31 German Yearbook of International Law 165,184 2 Gordon McCormick, Stranger Than Fiction: Soviet Submarine Operations in Swedish Waters (Rand, 1990), 4; see also Klein, n 14, 42; NB primary sources are in Swedish, hence reliance upon secondary, mainly US, sources in English 3 Ibid. 3-6 4 Ibid., and Ken Booth, Law, Force and Diplomacy at Sea (1985, Routledge Revivals, 2014) 130-136, who also noted similar problems for Norway 5 McCormick, n 47,16-17,23 6 Discussed later 7 n47 8 Ibid. 8
  • [2] Ibid. 7-9 2 Article 23 of the 1958 Convention by implication preserves sovereign immunity of warships by not prescribing the enforcement measures available to a coastal state which it provides for other categories of vessel. See discussion in Mane Jacobssen, ‘Sweden and the Law of the Sea’ in Tullio Treves and Laura Pineschi (eds), The Law of the Sea: The European Union and its Member States (Martinus Nijhoff, 1997) 495, 500, on Sweden’s strong emphasis on sovereign immunity of warships 3 This is consistent with the view expressed in the German Legal Basis for the Operations of Naval Forces, at 59, that sovereign immunity of a sunken warship is lost only if title is formally abandoned or after capture in an aimed conflict. The US Commander’s Handbook on the Law of Naval Operations takes essentially the same position at para 2.1.2. 4 McCormick, n 47,10-11 5 Ibid. 3-6
  • [3] Ibid, n 2 Ibid. 11-13 3 Ibid. 14 4 Ibid. 13 5 Ibid. 6 Ibid 1, 15-20 7 Ibid. 14-15 8 For a word of caution on the use of force in response to non-innocent passage by warships see Froman, n 46, 673-675; Booth, n 49, sees the law as ‘malleable’ in tins area, cituig D. P. O’Connell, The Influence of Law on Sea Power (Naval Institute Press, 1975) 142-145. In the pages cited, O’Connell hnnself elaborates in some detail that the practice of a number of NATO and Warsaw Pact nations was to attack submerged contacts, or at least force them to the surface. O’Connell is ambivalent about the legality of such actions, noting that
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