Implications of Hybrid Warfare for the Order of the Oceans

Ocean Governance Topic Week

By Alexander Lott


Since Frank Hoffman coined the term “hybrid warfare” in 2007,1 numerous articles and books have been written on this theme from the perspective of military studies and international relations.2 Yet the existing legal literature has not so far focused on the challenges that hybrid warfare poses for the order of the oceans. One of the main current research gaps lies in the lack of clear understanding on how the law of the sea operates in hybrid warfare.3

The principal question is how can the law of the sea contribute to ensuring the rule of law in major shipping routes impacted by hybrid warfare? Another fundamental research problem lies in the ambiguities of how hybrid naval warfare or conflict differs – if at all – from traditional concepts of naval warfare or law enforcement operations. The implications of hybrid warfare for ocean governance deserves to be examined, as well as the usefulness of the concept of hybrid warfare for assessing the (il)legality of an aggressor’s actions in the maritime domain.

Hybrid Warfare as a Challenge to the Rights of Navigation

The means of hybrid naval warfare include the use of firearms and explosives, arrests of ships, cyberattacks, threats of force, economic coercion, and grey maritime networks, to name a few.4 Its scope may also include industrial projects that cause ecological destruction and pose security threats in the maritime domain. Notable examples include the construction of the Kerch Strait Bridge in the Black Sea, subsurface Nord Stream pipelines in the Baltic Sea, and artificial islands in the South China Sea that are allegedly detrimental to the marine environment and are protested against by the coastal states that are impacted by these construction activities.

Coastal states may perceive such industrial projects in their adjacent waters as a threat to their national security. For example, Finland’s defense minister has referred to concerns that are largely shared with the neighboring Baltic States that Russia could use its armed forces during a conflict situation to control the Nord Stream pipelines that cross Finnish, Swedish, and Danish maritime zones.5 Ukraine has similar concerns in respect of the Kerch Strait Bridge and much of the international community in relation to the artificial islands in the South China Sea. These projects have also created new challenges for the rights of navigation in the relevant maritime areas and thus for the stability of the law of the sea.

In 2018, the volume of seaborne trade reached over 11 billion tons which accounts for approximately 90 percent of global trade.6 Hybrid warfare is a hindrance to navigation in important maritime routes and has a negative impact on the stability of global commerce. In particular, such challenges to the rights of navigation go against the strategic maritime security interests of the European Union (EU) and its member states, which are “[t]he preservation of freedom of navigation, the protection of the global EU supply chain and of maritime trade, the right of innocent and transit passage of ships and the security of their crew and passengers.”7 The United States shares these interests and, in pursuance of these aims, operates the freedom of navigation program for the protection of navigation rights. In the example of freedom of navigation operations carried out in the South China Sea this has primarily caused tensions with China. Similarly, United States warships have repeatedly encountered dangerous approaches from the Iranian navy vessels in the Persian Gulf and Russian warships and aircraft in the Baltic Sea.

Russia, China, and Iran are three states which are primarily associated with the adoption of techniques of hybrid conflict.8 They are also important law of the sea actors, whose maritime areas include or are proximate to strategic waterways.

It is estimated that the rate of crossings in the South China Sea amounts to more than half of the world’s merchant fleet capacity,9 and the Baltic Sea is an area where approximately 15 percent of global cargo is trafficked.10 The Baltic Sea, the South China Sea, the Strait of Hormuz, and the Black Sea are also strategically important routes for oil and gas shipments.11 The Baltic Sea, which is already heavily used for the export of Russian oil, is also destined to become the biggest route for the transportation of Russian natural gas to Europe, overshadowing the main alternative transit route in Ukraine.12 The Black Sea, which holds itself as much natural gas reserves as the North Sea, is used by Russia as one of its main routes for oil shipments and is also destined to become crossed by many subsurface pipelines.13 Furthermore, the Strait of Hormuz is one of the main global chokepoints for the transportation of oil. Approximately a fifth of global oil exports are shipped via the Strait of Hormuz.14

The strategic importance of these maritime regions shows how significant it is to uphold the rule of law and safeguard the passage rights therein. However, these maritime regions are also areas where the stability of navigation is currently under pressure due to the coastal states’ shifting security considerations and methods of hybrid conflict. Foreign ships that were navigating through important chokepoints of maritime commerce have recently repeatedly been subjected to the use of force or coercion by some coastal states. Notable examples include the Kerch Strait incident of November 25, 2018, and the Strait of Hormuz incidents in the summer of 2019. 

Regional Examples of Grey Zones in Maritime Hybrid Conflict

The grey zone in hybrid warfare can be understood as a space short of clear-cut military action wherein the aggressor creates enough ambiguity to reach its strategic objectives without engaging in an open offensive.15 In the Kerch Strait incident of November 2018, Russia arguably made use of legal uncertainty by operating in a grey zone for complicating decision-making for other states. It seized three Ukrainian naval ships, including two warships, and arrested their crew as they were entering the Kerch Strait under freedom of navigation. In the context of the annexation of Crimea and armed conflict in eastern Ukraine, this incident has raised the question of whether Russia’s actions in the Kerch Strait should be considered as being undertaken in the legal framework of international humanitarian law.16 In other words, it is not entirely clear to what extent the law of the sea applies in hybrid warfare or conflict. This is intertwined with the question of whether the law of naval warfare or the legal framework on law enforcement should be applied in so-called grey areas to assess the legality of the coastal State’s use of force or direct coercion on the sea.

In the Kerch Strait incident Russia acted openly by using its Coast Guard vessels. By contrast, in the attacks against two oil tankers at the approaches to the Strait of Hormuz in the summer of 2019, the aggressor used a covert operation. In the context of the South China Sea, China’s activities in a grey zone allegedly include both elements, such as the use of law enforcement and a maritime militia in an escalatory manner to deter the use of natural resources by other states.17

As widely acknowledged, the passage rights of foreign ships and aircraft are at the center of tensions between China and the user states of navigation routes in the South China Sea.18 By contrast, Russia’s practice in relation to the passage rights of ships and aircraft in, above and near its maritime areas in the Baltic Sea (such as the eastern part of the Gulf of Finland and adjacent to the Kaliningrad enclave) has largely remained unnoticed in legal research. The repeated unsafe actions of Russian fighter jets against U.S. warships that have entered the Baltic Sea, the incursions of suspected Russian submarines into the territorial seas of Sweden and Finland, as well as the multiple violations of Estonia’s airspace by Russia’s aircraft are all instances that merit further attention in the context of hybrid conflict in the Baltic Sea region.19

In other occasions, tensions between the coastal states of the Gulf of Finland have had a direct adverse impact on the passage rights of ships. For example, in the aftermath of the 2007 riots which were sparked in the Russian-speaking minority in Tallinn due to the relocation of the Soviet Bronze Soldier monument, Russia declined to give its authorization for crossing its territorial sea under the right of innocent passage to the commercial ship Vironia. She transported goods and passengers in the eastern Gulf of Finland between the Estonian Sillamäe Port and the Finnish Kotka Port. Russia effectively caused the closure of the ferry line.

In practice, the Nordic States acknowledge the threats of hybrid warfare and actively prepare to counter such challenges in the northern Baltic region.20 For example, the first large-scale training exercise of the United Kingdom-led Joint Expeditionary Force was aimed at countering threats emanating from a hypothetical hybrid warfare in Estonia, including its maritime domain.21 Likewise, the Finnish defence minister has cautioned against the possibility that the demilitarized Åland Islands are turned into a theater of war by so-called little green men in case a foreign state is willing to breach the rules of international law.22

Legal Implications of Grey Zone in the Maritime Domain

The aggressor usually uses grey areas to complicate decision-making on the (il)legality of its actions in conflict situations and, from other states’ perspective, make it more difficult to take resolute steps in response. This is partly because it remains unclear what is the threshold for the applicability of the law of naval warfare in situations of hybrid conflict. Nonetheless, this does not necessarily mean that hybrid conflict should be subjected to a new set of rules. Usually, incidents that have occurred in grey areas in the context of hybrid conflict (e.g. the examples provided above) can be subjected to the legal framework of humanitarian law or peacetime law enforcement based on which it is possible to assess their legality.

Historians have pointed out that hybrid warfare is not a distinctly new phenomenon and, instead, simply constitutes a new term for a centuries-old concept.23 In the negotiations, drafting, and discussions during the process of creating the relevant treaties on the law of the sea and armed conflict, states did not consider it necessary to establish a separate legal framework for hybrid warfare. When drafting the relevant treaties, they instead proceeded from traditional concepts of laws of peace and war. Although rapid developments in technology have made it now possible to adopt more sophisticated means of hybrid warfare, including cyber warfare, states should still principally be able to classify any incidents of hybrid warfare under either the ramifications of armed conflict or peacetime law enforcement operations.

Any new legal framework for hybrid naval warfare that falls between the laws of peace and war would risk creating additional ambiguities in assessing the legality of the aggressor’s actions in the so-called grey area. Generally, where disputes arise over the interpretation of the applicable laws in situations concerning grey areas in whatever field of law, recourse is made to courts for justice and legal certainty. Similarly, one may expect that the current ambiguities regarding the classification of incidents which have occurred in grey areas in a hybrid conflict will gradually dissolve in the proceedings before international judicial bodies on a case-by-case basis.

In this context, the ongoing arbitral proceedings between Ukraine and Russia over the Kerch Strait incident of November 2018 are particularly promising. The International Tribunal for the Law of the Sea has found that “the distinction between military and law enforcement activities must be based primarily on an objective evaluation of the nature of the activities in question, taking into account the relevant circumstances in each case.”24 This question will likely be addressed in greater detail during the arbitral proceedings as instituted by Ukraine on April 1, 2019 under Annex VII to the Law of the Sea Convention25 on the Kerch Strait incident.26

Thus, instead of drafting new international rules on the so-called grey area in hybrid warfare or conflict, it might be feasible to first wait for international judicial bodies to develop their case law which would clarify the criteria for distinguishing between law enforcement operations in the maritime domain from naval warfare operations.

At the same time, states could modify their current domestic legal acts on national defense, law enforcement, and state of emergency in order to ensure that the key provisions on declaring a state of emergency or war and maintaining order in the maritime domain are sufficiently flexible for responding to the dynamic challenges of hybrid warfare. This may require amendments to domestic definitions such as those pertaining to a state of emergency or defense readiness. For example, maintaining in a domestic legal act a closed list of instances that constitute a threat to constitutional order (e.g. terrorist activity, forceful isolation of an area), and offer a prerequisite for a state to declare a state of emergency, might not enable it to proportionately tackle the irregular tactics and formations of hybrid warfare. This is especially the case where a state has defined the state of emergency via an outdated closed list of activities that are deemed to pose threat to its constitutional order. States that are located at the front line of hybrid warfare should consider making the threshold for declaring a state of emergency rather flexible.


Based on the incidents in the Black Sea, the Strait of Hormuz, the Baltic Sea, and the South China Sea in the past decade, one may reasonably argue that state practice demonstrates the increasing use of hybrid naval warfare techniques. Yet the acceptance of a new legal concept of hybrid conflict that falls between the fields of naval warfare and peacetime law enforcement could further complicate the already difficult assessment of the legality of the aggressor’s actions in the so-called grey area. A distinct legal framework for hybrid naval warfare would arguably create further legal ambiguity, rather than help solving current problems in distinguishing the law of peace from the laws of naval warfare. Hence, it might contribute to the aims of states that employ practices of maritime hybrid warfare.

States may wait for international judicial bodies to establish solid case law on differences between military and law enforcement operations in the context of hybrid conflict, including in the current proceedings on the Kerch Strait incident of November 2018. At the same time, states should revise their domestic legal acts where necessary for ensuring that the key provisions on declaring a state of emergency or war and maintaining order in the maritime domain are sufficiently flexible for responding to the dynamic challenges of hybrid warfare.

Dr. Alexander Lott is a postdoctoral fellow at the Norwegian Centre for the Law of the Sea at the University of Tromsø, the Arctic University of Norway. He is also a Lecturer of Administrative Law at the University of Tartu, Estonia.


1. F. G. Hoffman. Conflict in the 21st Century: The Rise of Hybrid Wars. Arlington 2007, p. 29.

2. C. Kremidas-Courtney. Countering Hybrid Threats in the Maritime Environment. – Center for International Military Security, 11.06.2018.

3. See also S. Haines. War at sea: Nineteenth-century laws for twenty-first century wars? – 98 International Review of the Red Cross 2016(2), pp. 419, 443-444.

4. C. Callaghan, R. Schroeder, W. Porter. Mapping Gray Maritime Networks for Hybrid Warfare. Center for International Maritime Security, 01.07.2020.

5. J. Niinistö. Itämeren geostrateginen merkitys kasvussa. Centrum Balticum, 02.03.2017.

6. UN Conference on Trade and Development. 2019 e-Handbook of Statistics. United Nations 2019.

7. Council of the European Union. European Union Maritime Security Strategy. Brussels 2014, pp. 6-7.

8. See, e.g. J. Stavridis. Maritime Hybrid Warfare is Coming. – 142 US Naval Institute Proceedings 2016(12).

9. Z. Keyuan. Navigation in the South China Sea: Why Still an Issue? – 32 The International Journal of Marine and Coastal Law 2017(2), p. 244.

10. HELCOM. Ensuring safe shipping in the Baltic. Helsinki 2009, p. 2.

11. Ministry of Defence. Future Security Challenges in the Baltic Sea Region: A study for the Swedish Armed Forces by the Development, Concepts and Doctrine Centre. Shrivenham 2015, p. 4.

12. G. Kuczyński. Nord Stream 2: A Trap for Ukraine. The Warsaw Institute Review, 10.02.2019.

13. M. Papatulica. Black Sea area at the crossroad of the biggest global energy players’ interests. The impact on Romania. – 22 Procedia Economics and Finance 2015, pp. 475, 478.

14. P. Nobakht. Why Does the Strait of Hormuz Matter? BBC News, 11.06.2019.

15. See Stavridis, supra n 8.

16. See J. Kraska. The Kerch Strait Incident: Law of the Sea or Law of Naval Warfare? EJIL: Talk!, 03.12.2018.

17. L. J. Morris et al. Gaining Competitive Advantage in the Gray Zone: Response Options for Coercive Aggression below the Threshold of Major War. The RAND Corporation, Santa Monica 2019, p. 92.

18. Keyuan, supra n 9, p. 245.

19. See further A. Lott. Le régime légal de la partie septentrionale de la mer Baltique dans le contexte des récents développements de sécurité. – Stratégique 2019(1-2), pp. 255-272.

20. C. S. Chivvis. Understanding Russian “Hybrid Warfare” and What Can be Done About It. The RAND Corporation, Santa Monica 2017, p. 7.

21. See V. Lauri. Salmistul toimub brittide meredessant. ERR Uudised, 29.06.2019. See also D. Cavegn. UK planning landing operations exercise in Estonia in summer 2019. ERR News, 09.12.2018.

22. Niinistö, supra n 5. R. Uosokainen. Puolustusministeri Niinistö: Demilitarisoituna Ahvenanmaa muodostaa sotilaallisen tyhjiön. Yle Uutiset, 17.10.2016.

23. P. R. Mansoor. Introduction: Hybrid Warfare in History, in W. Murray, P. R. Mansoor (eds.). Hybrid Warfare: Fighting Complex Opponents from the Ancient World to the Present. New York: Cambridge University Press 2012, p. 1.

24. International Tribunal for the Law of the Sea. Order: Case concerning the detention of three Ukrainian naval vessels (Ukraine v. Russian Federation), 25.05.2019, para. 66.

25. United Nations Convention on the Law of the Sea. Montego Bay 10.12.1982, e.i.f. 16.11.1994.

26. Annex VII Arbitral Tribunal. Dispute Concerning the Detention of Ukrainian Naval Vessels and Servicemen (Ukraine v. Russia). Case No. 2019-28.

Featured Image: Kerch Strait Bridge (Wikimedia Commons)

2 thoughts on “Implications of Hybrid Warfare for the Order of the Oceans”

  1. Maritime structures- such as mentioned in this article- are least inititially (and that is scientifically proven) detrimental to ecosystems, but some become habitats later after settling down to the local conditions, but certainly are not the same as they were before the interference occurred.
    Since leaving the RN in 1962 I have been involved with ecosystems both terrestrial and marine, and on various inoact surveys.
    No human activity in the seas is without consequences of various kinds, and some more serious than others, but constructions on both marine and land permanently impacts ecology.

  2. What about the actions of Turkey in the Mediterranean Sea? I don’t see any mention about that in the article. The Mediterranean is a lot more important for international navigation than the Black Sea, and still, no mention of that. It’s always a repetition of the same hybrid players, always excluding Turkey, which is actually one of the major hybrid players. Tunnel vision or denial?

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