Which Sub Ukraine Hit—and Why Russia Just Locked Down Its Main Black Sea Naval Base

Russian forces have blocked access to the Novorossiysk naval harbor following a Ukrainian Security Service (SBU) underwater drone strike on a Russian submarine, according to satellite imagery cited by the Crimean Wind partisan movement on December 17.

Satellite images show the entrance to the naval anchorage sealed with barges and boom barriers, measures intended to prevent Ukrainian surface and underwater drones from entering the harbor. While such defenses may reduce vulnerability to further attacks, they also effectively trap Russian vessels inside the base, complicating any rapid sortie into the Black Sea.

The closure comes days after an SBU underwater drone attack, carried out in coordination with the Ukrainian Navy, which critically damaged a Russian Project 636.3 Varshavyanka (Kilo-class) submarine inside the Novorossiysk base.

Defensive measures not entirely new—but timing is key

Norwegian analyst Thord Are Iversen noted that Russia has previously used barges and underwater barriers to protect its naval facilities in Novorossiysk. As evidence, he released a satellite image dated September 4 of last year showing similar obstructions at the harbor entrance.

Still, the timing of the renewed closure—immediately after the submarine strike—suggests heightened concern over Ukrainian underwater capabilities rather than routine force protection.

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Ukraine Just Did the Unthinkable to a Russian Sub—And There’s Likely No Fix

Dec 16, 2025 12:50

Which submarine was hit? OSINT answers

According to Defense Express, at the time of the attack, Russia had three operational Project 636.3 submarines in the Black Sea:

• B-265 Krasnodar;

• B-268 Veliky Novgorod;

• B-271 Kolpino.

Identifying the damaged vessel proved difficult. Since the start of Russia’s full-scale invasion, these submarines no longer display names or distinctive markings, making visual identification challenging.

The Kremlin attempted to downplay the damage by releasing tightly framed footage of the submarine, shot only after water had been pumped out.

However, a satellite image dated December 16 shows the vessel sitting more than a meter below its normal waterline—clear evidence of serious flooding prior to recovery efforts.

A single detail gave it away

That limited footage was still enough for Ukrainian OSINT analyst Duke BG to identify the submarine by examining a small marking near the stern hatch.

Among the three candidates, only B-271 Kolpino features a thin white outline in that specific location. The other submarines—Krasnodar and Veliky Novgorod—use a thicker circular marking. Additional vessels with similar markings are either not in the Black Sea or have already been destroyed, including B-237 Rostov-on-Don, which was sunk in occupied Sevastopol.

While it is theoretically possible that the marking was repainted, analysts note this would be highly unusual, as Russian submarines typically retain standardized paint schemes during routine maintenance.

Why Kolpino matters

If confirmed, the damage to B-271 Kolpino is particularly significant.

It is the newest of the Black Sea Fleet’s Varshavyanka submarines, commissioned on November 24, 2016.

Losing or sidelining it further shrinks Russia’s already depleted submarine force in the region—and removes another potential launch platform for Kalibr cruise missiles.

Second submarine may also be affected

Analysts are now turning to a more difficult task: identifying a second submarine located several hundred meters from the blast site. The explosion was powerful enough to gouge a crater roughly nine meters wide into the pier, raising the possibility that shockwaves damaged nearby vessels—potentially including sensitive sonar systems.

If confirmed, that would mark not just a tactical success, but a strategic escalation in Ukraine’s campaign against Russia’s Black Sea Fleet.

Earlier, reports emerged that Russia decided to scrap the K-132 Irkutsk, launched in 1988, a nuclear-powered cruise missile submarine once slated for a major weapons overhaul that was meant to transform it into a launch platform for Zircon hypersonic missiles, Oniks anti-ship missiles, and Kalibr cruise missiles.

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