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Russian Anti-Submarine Drills Near the Kuril Islands Mark Expanded Naval Activity Around Northern Japan.
Japan’s defense authorities reported a Russian Steregushchiy III–class corvette transiting the Tsugaru Strait toward the Pacific as Moscow conducted anti-submarine drills near the Kuril Islands. The activity highlights sustained Russian naval pressure along chokepoints critical to northern Japan and a continued emphasis on undersea warfare.
On 1 February 2026, the Japanese Ministry of Defense confirmed that a Russian Steregushchiy III–class warship, hull number 337, transited eastward through the Tsugaru Strait toward the Pacific Ocean. In the days that followed, Russia’s Pacific Fleet publicised anti-submarine warfare exercises conducted by the corvettes Gromkiy and Gremyashchiy in the straits of the Kuril Islands, including a simulated torpedo launch using the Paket-NK system. Together, the Japanese and Russian disclosures provide complementary perspectives on sustained Russian naval activity along key maritime approaches near northern Japan and highlight Moscow’s continued emphasis on undersea warfare in constrained and strategically sensitive waters.
The reported Russian warship transit through the Tsugaru Strait and subsequent anti-submarine drills near the Kuril Islands underscore sustained naval activity along strategically sensitive sea lanes north of Japan (Picture Source: Russian Navy / Tass / Amur Shipyard / Japanese Ministry of Defense)
Japan’s account presents a concise record of a specific movement and the associated surveillance posture. Around 08:00 on 1 February, the Japan Maritime Self-Defense Force (JMSDF) detected a Russian Navy Steregushchiy III–class frigate or corvette, hull number 337, approximately 130 kilometres west of Cape Tappi in Aomori Prefecture, proceeding southeast. The vessel was subsequently observed transiting eastward through the Tsugaru Strait into the Pacific Ocean. In line with established practice, the JMSDF assigned the escort ship Chikuma of the 15th Escort Division, based at Ominato, and a P-3C maritime patrol aircraft from the 2nd Aviation Group at Hachinohe to conduct surveillance and information collection throughout the passage. The communication is deliberately factual and neutral, reflecting Japan’s long-standing policy of publicly reporting foreign naval movements near its coasts as part of its broader approach to maritime domain awareness and transparency.
The Russian release, by contrast, is structured around a detailed training scenario. It states that the corvettes Gromkiy (Project 20380) and Gremyashchiy (Project 20385) of the Pacific Fleet conducted anti-submarine warfare tasks in the strait zones of the Kuril Islands while underway. During the exercise, the crews simulated the detection of a submarine belonging to a notional adversary that attempted to evade tracking. The ships practised tactical techniques for tracking the underwater contact and issued a signal ordering it to surface. After the simulated submarine did not comply, the combat team on board Gromkiy carried out an electronic (training) launch of a torpedo from the Paket-NK complex, representing the destruction of the target. In parallel, the corvettes conducted drills against modern threats from unmanned aerial vehicles and unmanned surface craft, engaging simulated targets with AK-630M 30 mm automatic close-in weapon systems and 12.7 mm heavy machine guns. The emphasis is on realistic but clearly scripted training, with the “enemy” submarine explicitly described as notional and the torpedo firing as electronic.
From a defense-analytical standpoint, the choice of platforms and systems is significant. Project 20380 and 20385 corvettes are multi-role surface combatants optimised for operations in coastal and near-sea zones, with a strong focus on anti-submarine warfare and self-defense within task groups. Their deployment in the Kuril straits underscores the importance attributed by Russia to these waters as access routes between the Pacific Ocean and the Sea of Okhotsk. On the Japanese side, Chikuma is an escort vessel suited to patrol and surveillance missions, while the P-3C is a long-range maritime patrol aircraft designed for anti-submarine warfare and sea surveillance. The pairing of a surface escort and a patrol aircraft reflects a layered approach to monitoring foreign warships transiting near Japan, with surface and air assets combining to maintain continuous tracking of movements through a key maritime chokepoint.
The Paket-NK complex merits particular attention in this context. It is designed as a close-in defensive and offensive system, combining short-range anti-submarine torpedoes with anti-torpedo interceptors to protect surface ships against both submarines and incoming torpedoes in confined waters. Training its use in a scenario where a submarine contact is tracked, ordered to surface, and then “neutralised” through an electronic torpedo launch reflects an emphasis on rapid decision-making and engagement procedures at short range. In narrow straits such as those of the Kuril chain, where distances are limited and acoustic conditions can be complex, systems like Paket-NK offer an additional layer of protection for surface combatants, complementing longer-range sensors and weapons. The explicit reference to Paket-NK in the Russian communication suggests that close-in anti-submarine and self-defense capabilities are considered central to the Pacific Fleet’s posture in this area.
Viewed from Tokyo, these developments occur in a maritime space that is both operationally active and politically sensitive. The Tsugaru Strait links the Sea of Japan to the Pacific and includes a corridor where the breadth of territorial waters is narrower than the width of the strait, allowing foreign warships to pass while remaining in waters considered international. Japan routinely monitors and publicly reports such transits, whether by Russian or other navies, as part of a wider pattern of transparency that also includes frequent reporting on airspace activity and fighter scrambles. The latest transit by hull 337, assessed as a modern Steregushchiy III–series ship, fits into this pattern of continued Russian naval presence near the Japanese archipelago. By assigning Chikuma and a P-3C and then publishing the information, Japanese authorities underline their focus on maintaining situational awareness and reassuring domestic and international audiences that movements in proximity to Japan’s main islands are observed, documented, and handled through standard procedures rather than crisis measures.
From the Russian perspective, the Kuril exercises highlight the priority accorded to protecting maritime approaches and supporting broader strategic concepts in the Pacific and Far East. The Kuril Islands form a chain of narrow straits that connect the Pacific Ocean with the Sea of Okhotsk, which Russian strategic thinking has often treated as a favourable area for the deployment of ballistic-missile and multi-role submarines. Training Gromkiy and Gremyashchiy in anti-submarine warfare, Paket-NK employment, and countermeasures against unmanned systems in these waters contributes to maintaining crew proficiency in environments where depth, currents, and traffic complicate undersea detection and tracking. It also mirrors other reported Pacific Fleet activities in the wider Asia-Pacific, where Russian corvettes have conducted exercises to search for and destroy mock submarines and to refine procedures for air defense and anti-sabotage tasks. In this light, the Kuril drills appear as part of a sustained effort to ensure that the Pacific Fleet can secure key straits and adapt to emerging threats such as UAVs and unmanned surface vessels.
The Japanese and Russian communications depict an increasingly sophisticated but still structured pattern of naval activity in northern waters. Japan continues to treat Russian ship movements through international straits near its territory as events to be monitored closely and reported transparently, relying on established surface and air assets to maintain maritime domain awareness. Russia, for its part, is using modern corvettes and systems like Paket-NK to refine its capabilities in anti-submarine warfare and counter-unmanned defense in and around the Kuril straits, and chooses to highlight these efforts in its public messaging. As both sides operate in proximity along narrow and strategically important sea lanes, professional conduct at sea, clear communication of intentions, and sustained transparency about exercises and transits will be essential to ensure that necessary training and lawful movements do not inadvertently aggravate tensions in an already complex regional security environment.
Written by Teoman S. Nicanci – Defense Analyst, Army Recognition Group
Teoman S. Nicanci holds degrees in Political Science, Comparative and International Politics, and International Relations and Diplomacy from leading Belgian universities, with research focused on Russian strategic behavior, defense technology, and modern warfare. He is a defense analyst at Army Recognition, specializing in the global defense industry, military armament, and emerging defense technologies.