Defense Alert: First Joint Russian Chinese Submarine Patrol Reshapes Asia Pacific Naval Balance.

On August 27, 2025, Russia’s Pacific Fleet confirmed that Russian and Chinese submarines have carried out their first-ever joint patrol in the Asia-Pacific region, marking a milestone in bilateral military cooperation. According to the fleet’s press service, the unprecedented deployment involved diesel-electric attack submarines navigating through the Sea of Japan and the East China Sea. The announcement, reported by the Russian Pacific Fleet, underscores a new phase in the consolidation of Sino-Russian naval interoperability at a moment of heightened strategic tensions in the Indo-Pacific.
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By extending their annual joint patrol framework to include submarines, Russia and China have moved one step closer to a full-spectrum naval partnership capable of challenging Western dominance in the Pacific (Picture source: Kremlin)

The patrol included Russia’s Project 636.3 Kilo-class submarine Volkhov (B-603), which covered more than 2,000 miles from its base in Vladivostok. The Project 636.3, often referred to by NATO as the “Improved Kilo,” is one of the quietest diesel-electric submarines in service, sometimes nicknamed the “black hole” due to its very low acoustic signature. Equipped with advanced sonar suites, Kalibr land-attack cruise missiles, and heavyweight torpedoes, the Volkhov is designed for anti-submarine and anti-surface warfare as well as land-attack missions, making it a highly versatile platform in littoral and open-sea environments.

While Russian sources did not officially disclose the model of the Chinese submarine participating in the patrol, imagery and analysis published at the beginning of August by the U.S. Naval Institute (USNI) identified the Chinese unit as the Great Wall 210, part of the People’s Liberation Army Navy’s fleet of Improved Kilo-class submarines acquired from Russia between 1997 and 2005. The PLAN currently operates ten of these boats, which remain central to its conventional undersea warfare capability. Like their Russian counterparts, these submarines are armed with heavyweight torpedoes and cruise missiles, making them capable of both coastal defense and offensive strike missions.

Both submarines operated in coordination with a wider task force, including the Russian corvette Gromkiy and the large anti-submarine ship Admiral Tributs, together with the Chinese destroyers Urumqi and Shaoxing and auxiliary support vessels. Rescue ships from both navies, Igor Belousov for Russia and Xihu for China, conducted joint evacuation and submarine rescue drills. This element of the exercise underscored the technical sophistication of the patrol, as submarine rescue operations require advanced equipment and precise interoperability between crews, highlighting that both navies are moving toward combined operations in highly complex domains.

Historically, Sino-Russian naval cooperation had been limited to surface vessels since the first joint maritime patrol in 2021. The integration of submarine assets marks a qualitative leap, adding a new layer to combined operations. The operational history of their cooperation includes high-profile drills such as the 2021 circumnavigation of Japan and recurring air and sea patrols in the Pacific and near Alaska. With the Maritime Interaction 2025 exercise in Vladivostok serving as the backdrop, the shift to submarine patrols reflects a deeper level of mutual trust and technical interoperability.

From an operational perspective, submarine patrols represent one of the most challenging forms of naval cooperation. Maintaining contact between submarines requires precise coordination, advanced communication protocols, and the ability to distinguish friend from foe in complex underwater environments. Russian commanders stressed the importance of anti-submarine warfare (ASW) and the monitoring of maritime communications during the drills, while Chinese analysts, quoted by Global Times, framed the patrol as evidence of growing strategic trust between both nations.

The strategic implications of this joint patrol extend beyond naval tactics. Geopolitically, the deployment sends a clear signal to the United States and its allies in the Indo-Pacific that Moscow and Beijing are willing to align their undersea forces in contested waters. Geostrategically, the patrol reinforces both countries’ claims to be guardians of stability in the Asia-Pacific while simultaneously projecting deterrence toward Japan, South Korea, and the U.S. Navy. Militarily, it lays the groundwork for combined undersea operations in wartime scenarios, enhancing the ability of both navies to defend sea lines of communication and protect offshore economic facilities.

This first-ever joint submarine patrol thus represents not only an operational achievement but also a calculated geopolitical statement. By extending their annual joint patrol framework to include submarines, Russia and China have moved one step closer to a full-spectrum naval partnership capable of challenging Western dominance in the Pacific. The fact that both navies relied on Kilo-class submarines, renowned for their quietness and lethality, further illustrates the seriousness of the maneuver. At a time when the Indo-Pacific is becoming the central arena of global naval competition, this patrol highlights the growing willingness of Moscow and Beijing to coordinate beneath the waves as well as on the surface.