Ukraine’s underwater strike signals a dangerous new chapter in naval warfare

An underwater drone strike carried out by Ukrainian forces has inflicted what may be one of the most serious blows yet to Russia’s Black Sea Fleet, raising uncomfortable questions not only for Moscow but for Western navies watching closely.

Ukraine’s Security Service said its special forces, working alongside the navy, used an unmanned underwater vehicle to hit a Russian Improved Kilo-class submarine while it was moored in the port of Novorossiysk. The target, valued at around £300 million, was struck alongside the jetty in what Kyiv described as the first successful combat use of a sub-surface kamikaze drone against a submarine.

Russia has played down the incident, insisting damage was limited. Footage released by Ukraine appears to show a significant explosion at the quay, suggesting otherwise. If confirmed, the loss would represent not just a destroyed vessel but the crippling of infrastructure intended to keep Russia’s fleet safe from attack.

A shrinking Black Sea Fleet

The submarine targeted was one of a small number of vessels capable of launching Kalibr cruise missiles, weapons used repeatedly against Ukrainian cities. Two such submarines are now believed to have been lost, leaving only a handful still operational.

That matters. These boats formed the backbone of Russia’s sea-based strike capability in the region and played a central role in threatening commercial shipping. Their removal further reduces Moscow’s ability to operate undetected in the Black Sea.

The strike also underlines a broader reality. Russia’s navy retreated to Novorossiysk after being pushed from its long-held base at Sevastopol in Crimea. That sanctuary now appears compromised. As one Western naval analyst put it, “There are fewer and fewer places left where Russian warships can assume they are safe.”

Why this attack is different

Surface drones have already reshaped the conflict at sea, but this underwater drone strike represents a more complex and dangerous evolution. Navigating an unmanned vehicle into a defended harbour, below the surface and without satellite navigation, requires advanced systems and careful planning.

How the drone was guided remains unclear. It may have relied on inertial navigation, seabed-mapping sonar, or a tethered communications link to a relay platform outside the harbour. Each option carries technical risks. Any of them succeeding marks a significant leap in capability.

What is striking is not just Ukraine’s ingenuity but Russia’s apparent failure to adapt. Warships and submarines were hit while stationary, simplifying the attacker’s task. Basic harbour defences, such as nets, sensors or patrols, appear either absent or ineffective.

Lessons closer to home

The implications extend well beyond the Black Sea. Western ports and naval bases are not immune to similar threats. Fixed infrastructure, energy terminals and ships at berth are all vulnerable to covert underwater approaches.

The UK’s own defence assessments have acknowledged growing risks from uncrewed systems, particularly in congested coastal waters. The Ministry of Defence has previously warned that critical maritime infrastructure requires improved monitoring as underwater technology becomes cheaper and more accessible.
For background on how navies are adapting to uncrewed systems, see this overview of maritime autonomous technology from the Royal United Services Institute.

The uncomfortable truth is that innovation is moving faster than defences. Ukraine, fighting for survival, has embraced that reality. Russia, despite years of warning, appears not to have done so.

Four years into the war, the balance at sea is no longer determined by size alone. Precision, imagination and the willingness to rethink old assumptions are proving just as decisive.

For more independent coverage of defence, security and international conflict with implications for Britain and Europe, follow EyeOnLondon. We’d welcome your thoughts in the comments.

[Image Credit | Dan Rosenbaum]

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