Russian fleet revives secret submarine base in Crimea

Ukrainian media report that the Black Sea Fleet of the Russian Navy may have reactivated a submarine base in the city of Balaklava, located on the Crimean Peninsula occupied by the Russian Federation. The base, designated as Object 825 GTS, recently served as a museum under the name Balaklava Underground Museum Complex.

After the illegal annexation of Crimea, the site even received the Russian Federation's Ministry of Defense Award in the Field of Culture and Art in 2021. The main attraction of the museum was the exhibition "Submarine Forces of the Black Sea Fleet 1944-1994," although there were other attractions as well, including displays dedicated to conflicts like the Crimean War.

The main "living" attraction was the S-49 submarine project 644RW. This not-very-large conventionally powered machine was used to test torpedo launchers of a 650 mm caliber, which explains the unusual "superstructure" on its bow. Decommissioned in 1995, the unit became the main part of the underground museum's exhibit in 2021. Since the underground base is a museum, how could it serve the Russian fleet?

Ukrainian media cite several sources, including a report by the Atesh Movement, a Tatar resistance organization operating in Crimea. According to the report, the Russian fleet is building engineering barriers to impede activities of Ukrainian forces, such as naval saboteur groups or unmanned motorboats.

Considering that the Balaklava port is not often used by Russian surface ships (although, for example, in 2022, Coast Guard patrol boats of the FSB were anchored in the bay), what else could the Russians be protecting if not the old base? Furthermore, the report somewhat vaguely mentions the reuse of the base for military purposes. And what is Object 825 GTS itself?

The object was built shortly after the end of World War II as an anti-atomic bunker for submarines. Balaklava was one of the bases naturally well-protected by a narrow, winding strait and rocky hills. From 1953 to 1961, an enormous underground complex was excavated, consisting of a channel measuring 1,975 feet in length, 26 feet in depth, and 39 to 72 feet in width, capable of housing up to seven submarines of projects 613 and 633.

The tunnels also housed fuel, lubricant, and ammunition storage. In peacetime, loading of ammunition or fuel transfer occurred outside, at the pier, but in the event of war, it could be done inside the tunnel after closing the entrance with a floating gate. A similar gate was placed at the second tunnel exit, leading directly to the open sea.

The complex also included external infrastructure, such as the mentioned pier and additional warehouses, as well as a repair and technical base, Object 820. Removing approximately 132,000 tons of rocks from inside Mount Tavros allowed for the excavation of a submarine base, protected against even a nuclear attack. Official information claims the base's interior could withstand a direct explosion of a bomb with a yield of up to 100 kilotons.

If Ukrainian media reports, actually from the Tatar resistance movement, are to be believed, the base would return to its original function. Indeed, operating submarines against Ukraine—whether for coastal blockade or missile attacks on land targets—would be simpler and cheaper for the Russians by using an advanced base rather than ports further from the theater of operations.

At the same time, practice has shown that operating with naval forces from Crimea is very risky—submarines usually lack any armament to secure a surfaced unit against missile or drone attacks, and even minor damage can hinder effective operations. For this reason, a base allowing covert submarine operations, well-protected against attacks of any kind, appears very attractive to the Russians. However, there is a catch.

The old museum piece S-49 is a small submarine. It is 251 feet long, 22 feet wide, and has an average draft of about 16 feet. Modern submarines, armed with Kalibr cruise missiles, like the Warsaw-class project 636.6, which could be new residents of the tunnels under Tavros, are indeed shorter (242 feet). However, modern submarines have much "fuller" forms: widths reach up to 32 feet, and the average draft is 20 feet.

Therefore, it is possible that modern Russian submarines simply will not be able to safely enter the base without additional work. Furthermore, it is likely that some of the original equipment was looted after the USSR collapsed. For now, Russian submarines are expected to remain at the slightly more distant Novorossiysk, although it cannot be ruled out that they might return to the old venue in a few years. It is not such an original idea, by the way.

Hiding ships, admittedly always quite large objects, is nothing new, and the idea has ancient roots: Carthaginians kept their large galleys in enormous hangars to protect them from the weather.

Today, the most famous are the German reinforced concrete bunkers for submarines (U-Boot-Bunker). The first conceptual work was conducted in Nazi Germany before the war broke out, but construction began only in autumn 1940. The first submarine shelters were built in Hamburg and Heligoland, and eventually in many different port cities in Germany and occupied France and Norway. Forced laborers were also involved in the construction.

Several types of bunkers were built: three were related to shipyard infrastructure and allowed for safe shipbuilding, and the fourth provided shelter for operational units. Until the use of Tallboy bombs (later also guided Bat and Disney bombs) weighing 5,300 pounds in August 1944, U-boats were relatively safe in their bunkers.

The most famous "underground" naval base is Musköbasen, belonging to the Swedish Navy. It was built between 1950 and 1969 on the island of Muskö as the new main naval base. The excavated tunnels are so impressively large (the highest tunnels are 131 feet tall) that they can shelter even surface ships, with the largest probably being the Halland-class destroyers (397 feet long, 3,079 tons displacement).

It was also shut down due to cost savings in 2005, but due to the threat from Russia, the Swedes reactivated it in 2019. Very similar bases were built after World War II in Yugoslavia, such as Vis and Brač, and along the Bay of Kotor. They fulfilled their function, protecting Yugoslav (and actually already Serbian) submarines and missile boats from NATO bombings during the Allied Force operation in 1999.