UK Navy tracks Russian Kilo-class submarine in UK waters.

The Royal Navy confirmed British forces conducted a three-day operation tracking the Russian Kilo-class submarine Krasnodar as it transited from the North Sea through the Strait of Dover and into the English Channel. The mission highlights NATO’s increasingly overt approach to maritime deterrence as Russian naval activity near Western waters continues to rise.

According to information released by the British Navy, on 11 December 2025, British forces executed a coordinated three day operation to track the Russian Kilo-class submarine Krasnodar and its accompanying tug Altay as the pair moved west from the North Sea, through the Strait of Dover and into the English Channel, before the shadowing task was handed to a NATO ally near Ushant off northwest France. The submarine remained on the surface despite stormy conditions, while UK aircrew stayed poised to shift instantly into full anti-submarine warfare if Krasnodar submerged.
Follow Army Recognition on Google News at this link

UK Royal Navy Merlin helicopters from RFA Tidesurge shadow the Russian submarine Krasnodar in the English Channel as UK forces step up surveillance amid rising Russian naval activity (Picture source: UK Navy).

At the tactical level, the operation showcased a deliberately visible, layered approach built around a specialist Merlin helicopter from 814 Naval Air Squadron embarked for the duration on the Royal Fleet Auxiliary tanker RFA Tidesurge. The Merlin Mk2 is configured to find and hold submarines at risk using dipping sonar, deployed sonobuoys, and onboard processing that lets a crew rapidly classify contacts and cue follow-on forces. If escalation ever demanded a kinetic option, Merlin’s core underwater punch is the Sting Ray lightweight torpedo, designed to counter submarine threats in both open ocean and littoral conditions, giving the helicopter a credible prosecute and engage pathway rather than a purely observational role. In Royal Navy language, the intent was deterrent clarity, with Lieutenant Commander David Emery stressing that maintaining an overt presence and continued overwatch of Russian vessels in UK waters is vital for national security.

RFA Tidesurge matters here not because it is a front-line combatant, but because it makes maritime persistence possible. The Royal Navy describes the 39,000-tonne Tide class as the largest ships in RFA service, built to sustain the Queen Elizabeth class aircraft carriers while also delivering fuel and water to Royal Navy, NATO, and allied warships worldwide. Just as importantly for coastal tracking tasks, Tide class tankers can operate Chinook, Merlin, or Wildcat helicopters, effectively turning a logistics platform into a mobile aviation base when tempo and geography demand it.

Krasnodar, a Project 636.3 Improved Kilo, is exactly the kind of conventional submarine that complicates NATO’s northern approaches. Publicly available specifications for the type cite a submerged displacement around 3,100 tonnes, an operational depth around 240 meters with a maximum near 300 meters, and endurance on patrol measured in weeks, all characteristics that favor stealthy sea denial. Armament is centered on six 533 mm torpedo tubes capable of firing heavyweight torpedoes and laying mines, and the class is also associated with Kalibr family cruise missile launch capability through the same tubes, a feature that broadens its threat spectrum from ships to shore targets depending on loadout and tasking. In this case, the Royal Navy reported no dramatic underwater chase because the submarine stayed surfaced, but the operational point for London is that tomorrow’s transit may not be so obliging.

The strategic driver is spelled out by the UK itself. The Royal Navy said the UK has seen a 30% increase in Russian vessels threatening UK waters over the past two years, a trend reinforced by recent government statements that explicitly link Russian activity to intelligence collection and seabed mapping. In late November, the Defence Secretary publicly called out the Russian intelligence ship Yantar for operating near UK waters and for mapping undersea cables, capturing the mood in Whitehall with the line “We see you. We know what you are doing. And we are ready.”

That focus on cables and seabed infrastructure is not rhetorical. A UK Parliament inquiry notes the UK has around 60 undersea cables connecting it to the outside world and carrying 99 percent of its data, making disruption a genuine national resilience scenario rather than a niche naval concern. In parallel, the government has unveiled Atlantic Bastion, a program intended to combine autonomous systems, AI, warships, and aircraft to protect undersea cables and pipelines against the sort of underwater threat set Russia can generate. The protected asset list also includes the hardest target of all, the UK’s continuous at sea nuclear deterrent enterprise centered on HMNB Clyde and RNAD Coulport, which the Royal Navy describes as home to the nation’s nuclear deterrent and the storage and handling hub for key elements of the Trident system.

Legally, Russian vessels may transit through these waters under international law, but legality does not remove risk. Under UNCLOS, submarines in a coastal state’s territorial sea during innocent passage are required to navigate on the surface and show their flag, while the rules differ in international straits under transit passage concepts, leaving navies to manage both law and ambiguity in real time. Against that backdrop, Moscow’s increased maritime presence serves multiple purposes, including routine repositioning, strategic signaling, intelligence collection opportunities, and the simple operational effect of forcing NATO to spend scarce aircrew hours and sensors on constant watch. For the UK, this three-day operation was less a one-off intercept and more a snapshot of the new normal in the Channel and North Atlantic approaches.