Russia’s secretive Khabarovsk nuclear-powered submarine has reportedly gone to sea for the first time, marking a significant step toward operational deployment of Moscow’s Poseidon nuclear underwater weapon. The Project 09851 vessel left Severodvinsk in northern Russia in mid-August and entered the White Sea for initial trials, according to Russian military sources and European media reports.
Russian military blogs placed the departure on August 16-17, although Moscow and the Sevmash shipyard, the only one in Russia producing nuclear submarines, have not publicly confirmed this. The roughly 10,000-ton submarine was built specifically to transport Poseidon underwater drones, making it a key part of Russia’s effort to develop systems capable of bypassing existing missile defenses. Khabarovsk was formally unveiled in November 2025. Sea trials are the next major stage before the submarine can enter operational service.
Russia’s Khabarovsk submarine designed around the Poseidon system
Unlike conventional ballistic missile submarines, Khabarovsk was designed from the outset around Poseidon. Open-source assessments suggest it may carry up to six such weapons. Poseidon is a large, autonomous, nuclear-powered underwater drone capable of carrying a nuclear warhead over intercontinental distances.
Naval analyst H.I. Sutton reports that Khabarovsk’s Poseidon launch and storage systems are located in the submarine’s forward section. The vessel is the first submarine class purpose-built to carry Poseidon, while the Belgorod was modified for the system. Russia has released few verified technical details about either submarine, leaving much of their capabilities subject to open-source assessment.
🚨🇷🇺 Russia's Submarine Built To Launch Poseidon Nuclear Drones Begins Sea Trials
Russia’s Project 09851 Khabarovsk special-purpose nuclear submarine appears to have begun its first factory sea trials after being photographed leaving Severodvinsk on August 17. The voyage takes… pic.twitter.com/XupJFC90cV
— Military Summary (@MilitarySummary) August 24, 2026
What is Russia’s Poseidon nuclear underwater drone?
Russian President Vladimir Putin publicly introduced Poseidon in 2018 as a drone designed to function as a strategic nuclear weapon to overcome Western defenses. Unlike an intercontinental ballistic missile, Poseidon would approach targets underwater. Its nuclear propulsion system is extremely long range and allows the vehicle to travel across oceans without a crew.
Reported estimates put its range at more than 6,000 miles (9,600 km), with an operating depth of roughly 3,280 feet (1,000 meters). Those figures rely largely on Russian claims and open-source analysis rather than independent verification. The weapon could potentially strike ports, naval facilities, and coastal infrastructure while avoiding missile-defense systems built to intercept ballistic threats. Moscow has also promoted claims that an underwater nuclear detonation could generate destructive waves against coastlines, although experts dispute the more extreme “nuclear tsunami” scenarios.
Sea trials amid rising Russia-UK tensions
Khabarovsk’s reported first voyage comes amid renewed tension between Moscow and London over Britain’s military support for Ukraine. Russian officials have recently warned Britain of consequences after reports that British-made drones were used in Ukrainian strikes within Russia.
Foreign Minister Sergei Lavrov said Moscow could increasingly regard Britain as a participant in the conflict because of its support for Kyiv. The Russian Embassy in London has issued similar warnings, while British Prime Minister Andy Burnham said the UK would continue supporting Ukraine. Russian state television commentators have also invoked Poseidon while discussing possible retaliation against Britain. Such remarks do not represent official nuclear policy, but they illustrate the weapon’s growing role in Moscow’s strategic messaging.
How serious is the threat?
Defense specialists generally regard Poseidon as a genuine strategic capability but remain cautious about some of the more dramatic claims surrounding it. Its principal advantage is its underwater delivery method. Existing missile-defense systems are not designed to intercept a nuclear weapon traveling beneath the ocean rather than through the atmosphere. That does not make Poseidon undetectable. A large, fast-moving underwater vehicle could produce acoustic or thermal signatures detectable by anti-submarine systems.
NATO navies operate submarines, surface ships, maritime patrol aircraft, and underwater sensors designed to track such threats. Poseidon’s effectiveness will therefore depend heavily on how quietly it can operate and how difficult its reactor and propulsion system are to detect. Publicly available information remains insufficient to determine how successfully Russia has solved those engineering challenges.
🇷🇺 RUSSIA’S POSEIDON SUBMARINE ENTERS SEA TRIALS
Russia’s Project 09851 Khabarovsk, the first submarine designed from the outset to operate the Poseidon nuclear powered underwater drone, appears to have begun factory sea trials after leaving Severodvinsk on August 17.
The move… pic.twitter.com/4bOFRTbtUk
— Defense Intelligence (@DI313_) August 19, 2026
A cold war concept revived
The idea behind Poseidon is not new. Soviet planners explored large nuclear torpedoes during the early Cold War, including concepts intended for attacks against naval bases and coastal targets. The technology of the period, however, could not provide the necessary range and compact nuclear propulsion. Russia revived the concept decades later as concern grew in Moscow over the expansion of US ballistic missile defenses.
Poseidon emerged alongside other unconventional systems, including the nuclear-powered Burevestnik cruise missile, as part of a broader strategy to preserve Russia’s ability to retaliate even if traditional missile systems became more vulnerable to interception.
Russia’s Khabarovsk submarine brings Poseidon closer to deployment
Russia has previously outlined plans for multiple Poseidon weapons and several submarines capable of transporting them, although the precise status of the program remains unclear. Khabarovsk is central to that effort because it is the first submarine designed specifically as a dedicated Poseidon carrier.
Before entering service, the vessel must complete factory and state trials covering propulsion, navigation, communications, diving performance, and weapons systems. Its reported appearance in the White Sea therefore does not mean Russia already has a fully operational Poseidon force. It does show, however, that one of Moscow’s most closely watched strategic weapons programs has moved into a new phase of testing likely to draw attention from NATO navies and intelligence services.
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