Key Points – The Russian Navy has reportedly received the Yakutsk, the sixth and final submarine of its improved Project 636.3 Kilo-class, which will be deployed to the Pacific Fleet.
-The Kilo-class, a diesel-electric attack submarine first introduced by the Soviet Union in 1980, has been a cornerstone of Russia’s undersea fleet and a successful export.
Kilo-Class Submarine. Image Credit: Creative Commons.
-Nicknamed the “Black Hole” by NATO for its quiet operation, later variants were upgraded to launch Kalibr cruise missiles.
-Despite its longevity, the Kilo-class is being replaced by the newer but technologically troubled Lada-class, ensuring the Kilo’s continued service for years to come.
Russia’s Kilo-Class Submarine Has Reached the End
In June 2025, the Russian Navy reported that it had received its final Kilo-class submarine. The Yakutsk is the sixth and final Project 636.3 “Varshavyanka”-class (NATO reporting name Kilo-class) and is expected to be deployed in the Pacific Ocean, where Russia has been building up most of its assets.
The deployment of the Yakutsk in the Pacific signals a growing increased in Russian naval activity as tensions heighten between Russia and NATO. The Kilo-class has long been a cornerstone of Russia’s submarine fleet and still remains one of Russia’s most stealthy attack subs.
History of the Kilo-Class
The first Kilo-class submarine, B-248, was laid down by the Rubin Design Bureau in the Soviet Union in 1979 and commissioned in 1980. This marked the beginning of a long production run that would see the construction of dozens of submarines for both the Soviet Union and foreign navies.
The Kilo-class was notable for its teardrop-shaped hull, which was optimized for underwater performance, and its double-hull construction, which provided enhanced buoyancy and survivability. These submarines were designed for anti-submarine and anti-surface ship warfare, as well as reconnaissance and patrol missions.
The Kilo-class was designed to replace the Tango-class subs, which were larger and less stealthy than their successors. The Soviets built around 20 Kilo-class subs for their fleet before the dissolution of the USSR. Some subs were exported to India, China, and Iran, while most stayed in service with the Russian Navy. The original variants were designed for anti-shipping and anti-submarine operations in shallower waters. The Kilo-class was also well equipped to perform a wide variety of other missions as needed, such as mine laying or intelligence collection.
One of the defining features of the Kilo-class was its diesel-electric propulsion system, which allowed for quiet operation, a critical advantage in submarine warfare. The submarines were equipped with six 533 mm torpedo tubes capable of launching torpedoes, mines, and cruise missiles. They also featured advanced sonar systems, including the MGK-400 Rubikon sonar suite, and had an operational depth of up to 300 meters with an endurance of about 45 days. Due to their low acoustic signature, NATO nicknamed them “Black Holes,” a testament to their stealth capabilities.
Kilo-Class Submarine Like China
Why the Kilo-Class is Still Reliable
Over the years, the Kilo-class underwent several upgrades, resulting in three main variants. The original Project 877 was the baseline model introduced in the early 1980s. It featured basic sonar and combat systems and was exported to several countries, including India, China, Iran, and Algeria. The next major upgrade came in the 1990s with Project 636, known as the Improved Kilo.
This version featured enhanced sonar, quieter propulsion, and improved weapon systems, including the ability to launch Kalibr cruise missiles, which significantly extended its strike range. The most advanced version, Project 636.3, also known as Improved Kilo II, entered service in the 2010s. It included further improvements in stealth, electronics, and weapons, and is currently in service with the Russian Navy and several foreign navies, including Vietnam.
The Kilo-class has seen extensive operational use. In the Russian Navy, these submarines have been deployed in the Northern, Baltic, Black Sea, and Pacific Fleets. They played a notable role in the Syrian conflict, where they launched Kalibr cruise missiles against targets from the Mediterranean Sea.
Other countries have also used Kilo-class submarines effectively. India operates a customized version known as the Sindhughosh-class. China acquired several units and later developed its own Type 039A Yuan-class submarines, which were heavily influenced by the Kilo design. Vietnam purchased six Project 636.1 submarines, significantly boosting its naval capabilities in the contested South China Sea.
The Kilo-class has several strengths that have contributed to its longevity and popularity. Its stealth capabilities make it difficult to detect, and its versatility allows it to perform a wide range of missions. Additionally, it is more affordable than nuclear-powered submarines, making it an attractive option for countries looking to enhance their naval capabilities without the high costs associated with nuclear propulsion. However, the Kilo-class also has limitations.
Its diesel-electric propulsion system restricts its underwater endurance compared to nuclear submarines, and despite numerous upgrades, the basic design dates back to the 1970s, making it increasingly outdated in the face of modern threats and technologies.
Replacement by the Troubled Lada-Class
The Kilo-class was intended to be phased out in favor of the newer Lada-class submarines. The Lada-class was a significant technological advancement over the Kilo-class. It was designed to be even quieter and more efficient, with a reduced acoustic signature and advanced sonar and combat systems. One of the most anticipated features of the Lada-class is its air-independent propulsion (AIP) system, which would allow the submarine to remain submerged for longer periods without surfacing. This capability would significantly enhance its stealth and operational effectiveness.
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The lead boat of the Lada-class, B-585 Sankt Peterburg, was launched in 2004. However, the program faced numerous delays and technical challenges, which slowed its progress. As a result, the Russian Navy continued to rely on the improved Kilo-class submarines while the Lada-class underwent further development and testing.
Currently, 12 boats are planned to be put into service but so far only three have been completed, one of which has already been retired. Two Lada-class subs are currently under construction and are expected to enter service in 2025 and 2026. Despite these setbacks, the Lada-class is still intended to eventually replace the Kilo-class in Russian service, offering a more modern and capable platform.
About the Author:
Isaac Seitz, a Defense Columnist, graduated from Patrick Henry College’s Strategic Intelligence and National Security program. He has also studied Russian at Middlebury Language Schools and has worked as an intelligence Analyst in the private sector.
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