19 March 2023

Tackling the Underwater Threat: How Ukraine Can Combat Russian Submarines

Dr Sidharth Kaushal and Dr Kevin Rowlands

Given that building anti-submarine warfare capabilities along Western lines would require significant time and resources, how can Ukraine best counter the Russian submarine threat?

One of the signal successes of the Ukrainian armed forces has been denying the Russian Black Sea Fleet’s surface vessels the ability to operate in close proximity to Ukrainian shores. The successful attack on the fleet’s flagship, the Moskva, with indigenous Neptune anti-ship cruise missiles and the subsequent Russian defeat at Snake Island denied the fleet the air cover it needs to be able to operate in range of an increasingly credible Ukrainian anti-ship missile threat. As such, it may prove increasingly difficult for Russia to enforce a renewed surface blockade of Ukraine if it decides that inflicting economic harm is important – a likely assumption if the war of attrition continues over the longer term.

That being said, Russia does have other options with which to menace Ukraine’s maritime economy. The risk posed by naval mines represents one vector; another is the use of submarines, which have not featured significantly in the conflict thus far. The Black Sea Fleet’s force of four Project 636 (Kilo) and Project 877 (Improved Kilo) submarines have not been used in a blockading role to date, acting primarily as a launch platform for 3M-14 Kalibr cruise missiles. However, if Russia did decide to use them in this capacity, it would raise new challenges for Ukraine’s sea denial strategy, which thus far has had to contend primarily with the (comparatively) easy task of anti-surface warfare. The skills and capabilities needed for Ukraine to conduct anti-submarine warfare (ASW) along Western lines would be time-consuming and expensive to generate, and are unlikely to be acquired in the foreseeable future, begging the question of how to ‘do’ ASW on a shoestring.

The Relevance of the Black Sea Fleet’s Kilo-Class Submarines

In the immediate term, and for good reason, Ukraine’s priorities are likely to remain primarily land-focused. However, should the conflict reach a point of enduring, frozen stalemate, Russia may shift its military focus to wearing down the Ukrainian economy, which has already seen a 30% reduction in GDP. To an extent, this has been visible in the air and missile campaign witnessed over the winter. Moreover, it would follow a pattern of how belligerents attempt to secure a strategic breakthrough when a tactical battlefield breakthrough seems unlikely – with precedents such as the Iran–Iraq tanker war and the British blockade of Germany during the First World War.

To an extent, one might argue that Moscow does not need military force to inflict a de facto blockade – simply declaring that it has pulled out of the grain deal, for example, would likely cause insurance rates to spike to exorbitant levels. However, two alternative scenarios might be considered.

First, Moscow may wish to drive a spike in insurance costs without paying the diplomatic price for pulling out of the grain deal. A deniable attack could be facilitated by the Kilo-class submarines. The boats can clandestinely lay up to 24 naval mines each during a single sortie. A direct torpedo attack would be more audacious, but it is worth recalling the time it took to attribute North Korea’s sinking of the South Korean vessel Cheonan in 2010 – four months – by which time the initial international outrage had abated. Attacking a vessel carrying a volatile substance such as ammonium nitrite might offer a level of deniability which, however implausible, could preclude unambiguous attribution. To consider the impact of such action, we might consider that in 2019, insurance rates in the Strait of Hormuz rose tenfold after Iran’s limpet mine attacks – even though a convoy system was put in place.

Any effort to maintain Ukraine’s viability in the long term will depend on the ability of its economy to at least partially recover from the impact of war, and open sea lines of communication will be crucial

Second, the Black Sea Fleet’s submarines are an important launch platform for Russian cruise missiles such as the 3M-14 Kalibr, which – according to some experts – came close to delivering a death blow to Ukraine’s energy grid this winter. Any effort to maintain Ukraine’s viability in the long term will depend on the ability of its economy to at least partially recover from the impact of war, and open sea lines of communication will be crucial. The Black Sea Fleet’s submarines thus represent a clear and present challenge which the Ukrainian navy will need to resolve.

The Challenge of ASW

There are, however, be a number of issues that will preclude any effort to transpose a Western approach to ASW to Ukraine in the medium term. First, the platforms involved are too expensive and small in number to be gifted. Assets such as the P-8 maritime patrol aircraft or specialist ASW frigates are unlikely to be transferred, and the Ukrainian armed forces would struggle to crew, operate and protect them in any case.

ASW is an inherently skill-intensive task. Training an aviator on a Royal Navy Merlin helicopter, for example, takes at least 11 months before they can be integrated into frontline squadrons, and training pipelines everywhere are well known to be at capacity already. Training times for sonar operators are similarly long. Moreover, this excludes the challenge of integrating personnel into coherent units that can operate in tandem with one another. Though the Ukrainian navy had 11,000 personnel in its service when the war began, the fact that it had lost much of its fleet after 2014 – as well as an understandable focus on events on land – raises questions about the speed at which necessary competencies can be built, or rebuilt, within the force.

Finally, the maintenance of the platforms needed to operate an ASW barrier along Western lines would strain capacity at Ukrainian facilities, particularly if they remain under bombardment.

As such, a solution to the challenge of ASW – at least in the near term – needs to be developed along fundamentally different lines from traditional, Western approaches.
Begin with the End State, Not the Platform

There could, however, be relatively cost-effective solutions to the challenges that Ukraine faces. These could be built on the principle that harassment, rather than sea denial, should be the immediate Ukrainian goal. It is not necessary to destroy Russia’s submarines if they can be prevented from doing operationally useful work.

While the ideal of denying areas to Russian submarines is unlikely to be achieved, Ukraine can impose a set of conditions which will strain both vessels and crews

As a working hypothesis, it is reasonable to assume that Russian sabotage or interdiction of shipping to Ukraine is likely to occur within or close to Ukraine’s exclusive economic zone in the northern Black Sea, both to signal intent and because damaging vessels in a warzone is likely to be less contentious to the international community than sinking them well within international waters. If this is the case, the geography of the northern Black Sea offers partial solutions. The average depth of the area – 200 metres – is less than the 240-metre depth at which the Kilo generally operates, meaning that navigation and operation will be more difficult for submarines. This is not to say that it is impossible, and some parts exceed the average depth. However, submarines operating in the northern Black Sea do so at increased risk of collision, grounding and detection. The passage of submarines can be made even more risky by seeding the areas within which they can operate with remotely activated mines such as the US Hammerhead. Because these mines can be remotely activated, they are compatible with international law, and the fact that they can be programmed to seek specific magnetic anomalies aids against target misidentification. This would force the Kilos to operate in even shallower waters, increasing their risk even further.

Beyond canalising submarines through mines, Ukraine could use uncrewed capabilities to harass them further. For example, UAVs operating dipping sonobuoys and lightweight torpedoes could be utilised in an ASW role – an avenue that multiple navies are pursuing, albeit experimentally. While accurate detection by a UAV thus equipped may not be certain, a responsible submarine commander would have to take evasive action if he or she detected a pinging sonar, potentially disrupting firing solutions, affecting the vessel’s endurance, or even putting it in navigational danger. The perception that a UAV is armed and primed to attack could be exacerbated if some UAVs were equipped with munitions while many more were equipped with decoys that simulated the acoustic profile of an attack. We might think of the impact that the US Navy’s Julie Jezebel sonobuoys – which simulated the noise profile of a depth charge – had on Soviet submariners during the Cuban missile crisis.

Russian submariners’ perceptions of operational risks could also be compounded if Ukraine were to take possession of even a very limited number of ASW helicopters. Finally, the presence of NATO or other intelligence gathering aircraft, including P-8s, over the Black Sea would force Russian commanders to consider the possibility that Ukrainian assets were being cued, which – whether true or not – could be reinforced by conducting UAV flights at times at which the aircraft are present. Ultimately, all of these actions would raise the perceived risk for Russian operators and slow the rate and tempo of their activity.

There are no perfect immediate-term solutions to the submarine challenge. In the long term, after the war’s conclusion, Ukraine might well consider meeting the goals set out in its 2019 naval strategy, including rebuilding a surface fleet capable of limited sea control in peacetime, as well as prosecuting ASW missions near its shores and other sea denial missions. In the meantime, while the ideal of denying areas to Russian submarines is unlikely to be achieved, Ukraine can impose upon the Kilos and their operators a set of conditions which – though they may not end the submarine threat – will strain both vessels and crews. The immediate goal guiding Ukrainian ASW, then, should be harassment.

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