Key Points and Summary: The Kilo-class submarine program, launched during the Cold War, remains one of Russia’s most successful naval ventures.
-Known as “black holes” for their stealth, these diesel-electric subs excel in coastal operations, offering versatility and reliability. Modernized versions, like the Project 636.3 “Improved Kilo,” feature advanced sonar, quieter engines, and Kalibr cruise missiles, extending their range and offensive capabilities.
-The Kilo-class has also been a cornerstone of Russia’s defense exports, attracting buyers like China, India, and Algeria.
-Despite its success, challenges from Russia’s focus on land warfare and industrial constraints may impact the Kilo-class’s future production and export viability.
Kilo-Class Submarines: Russia’s Quiet Black Hole of the Seas
The Kilo-class submarine program, initiated by the Soviet Union during the Cold War and now inherited by the Russian Federation, has become one of the most successful submarine projects in Soviet — now Russian — history, serving the Russian Navy’s needs and the international export market.
In fact, many press reports claim this submarine is called the ‘black hole’ by many naval experts for its quiet undersea operations.
First introduced in the early 1980s, these diesel-electric submarines are remarkable for their stealth, reliability, and adaptability and are best known in the West by their NATO reporting name, “Kilo.”
The Kilo-Class Design
The Kilo-class design emphasizes success in littoral and coastal waters, nearer to shore, which are crucial for anti-shipping missions.
The subs are relatively diminutive in size, with a modest, appropriate 3,000-ton displacement. They feature six torpedo tubes capable of launching a mix of torpedoes and missiles, including the Kalibr cruise missiles.
This onboard weapon suite allows them to engage surface ships and submarines and support troops on land.
It is optimized for littoral, near-to-shore missions.
Research and Development
The development of the Kilo-class reflected the Soviet Union’s need for a submarine that could operate effectively near the coasts and in other relatively constrained maritime environments.
Key considerations included simplicity of maintenance, cost-effectiveness, and the ability to integrate more advanced technologies as they went online.
Modern Kilo-class submarines, such as the Project 636.3 “Improved Kilo” series, incorporate significant advancements over their predecessors.
They have improved sonar systems, more powerful and quieter engines, and an enhanced weapon suite.
Notably, the Kalibr missile system gives the subs an expanded offensive range and, therefore, a strategic role, capable of hitting targets on land up to 2,500 kilometers away.
These upgrades have allowed the Kilo class to remain relevant despite the introduction of newer submarine classes.
“All Kilo-class submarines are fitted with six 21-inch bow torpedo tubes that can launch torpedoes or naval mines. Many Kilo-class submarines have been outfitted to launch the Kalibr/Klub family of missiles from their torpedo tubes for long-range land attack (3M-14) or antiship (3M-54) operations,” the U.S. Naval Institute explains.
“The submarines have space to carry a maximum of 18 torpedoes or 24 naval mines. Only four Kalibr missiles reportedly can be included as part of the Kilo armament mix. Russia’s Improved Kilo II–class submarines first conducted long-range attacks against Islamic State targets in Syria in 2015. Since 2022, Russian Black Sea Fleet 636.3 submarines have made extensive use of the Kalibr missile to attack Ukraine.”
At Home and Abroad
The Kilo-class has been a cornerstone of Russian defense exports internationally, with dozens of hull units sold to a number of countries, including China, India, Vietnam, and Algeria.
The Kilo’s affordability, relative ease of operation, as well as its simplicity, and reliability have made it an attractive choice for countries in the market for a modest but powerful submarine capability, willingness to forgo nuclear propulsion, and the very bleeding edge of submarine technology.
The Kilo-class remains in production, with Russia continuing to build units both for its navy and for export. However, the future of the class faces challenges.
Though Russia is the inheritor of the USSR’s formidable underwater know-how, Russia’s ongoing war in Ukraine has reoriented the nation’s defense industry away from platforms and projects that do not directly affect the land war aspect.
The Kilo’s continued success in the international export market is an open question, as industrial constraints and limits to naval production will not disappear in the foreseeable future.
Kilo-Class: A Submarine Photo Essay

Pictured is a Kilo-Class Russian Submarine in the English Channel. The image was taken from Royal Navy Wildcat HMA2 Helicopter of 815 Naval Air Squadron. Kilo class is the NATO reporting name for the diesel-electric attack submarine.

Kilo-class Submarine. Image Credit: Creative Commons.

Iran’s Navy Has Kilo-Class Submarines. Image Credit: Creative Commons.

A Russian-built, Kilo-class diesel submarine purchased by Iran, is towed by a support vessel in this photograph taken in the central Mediterranean Sea during the week of December 23. The submarine and the support ship arrived at Port Said, Egypt, on Tuesday and were expected to begin transiting the Suez Canal today, Jan. 2, 1996. Ships and aircraft from the U.S. NavyÕs Sixth Fleet are tracking the submarine, which has been making the transit on the surface. This is the third Kilo-class submarine the Iranians have purchased from Moscow. DoD photo

Kilo-class Submarine. Image Credit: Creative Commons.

Kilo-class Submarine.
About the Author: Caleb Larson
Caleb Larson is an American multiformat journalist based in Berlin, Germany. His work covers the intersection of conflict and society, focusing on American foreign policy and European security. He has reported from Germany, Russia, and the United States. Most recently, he covered the war in Ukraine, reporting extensively on the war’s shifting battle lines from Donbas and writing on the war’s civilian and humanitarian toll. Previously, he worked as a Defense Reporter for POLITICO Europe. You can follow his latest work on X.
