Russia’s enormous Oscar-class nuclear attack submarines, known as the Project 949A, were designed during the Cold War with a specific mission in mind: to go hunting for American aircraft carriers, the pride of American naval power.

Because each U.S. flattop is protected by its own little fleet of escorting warships—many of them specialized in antisubmarine warfare—the Oscar’s primary game plane isn’t to creep up close for a torpedo attack.

Instead, it’s designed to lob enormous anti-shipping cruise missiles (ASCMs) from hundreds of miles away.

Cruise-missile submarines, designated SSGs and SSGNs by the U.S. Navy, were not a new concept. The earliest missile subs were adapted from more conventional submarines in the 1950s, and the Soviet Echo class, commissioned in 1961, were the first ones designed to employ cruise missiles as their primary armament.

Work on a large third-generation cruise-missile submarine, designated as the Project 949 Granit, began in the mid-1970s. It featured a double-hulled design, as was standard on large Soviet submarines. The primary hull with the crew compartments and ship systems is contained inside a more aquadynamic outer hull of thin steel. On those Oscar IIs still in service, the outer hull is separated by up to six feet or as little as two inches, depending on the location. Two nuclear reactors generated seventy-three megawatts of electricity for the enormous submarine. A crew complement of around one hundred occupied nine or ten compartments that could be sealed off from one another.

The Oscar class is large, in order to carry its heavy armament. The main production model is more than one and a half football fields long (154 meters), and displaces 12,500 tons while surfaced, making it the fourth-largest submarine type ever produced. Nonetheless, Oscar-class subs can attain an excellent maximum speed of thirty-seven miles per hour while submerged, and dive up to five hundred meters. However, they are reputed to be slow to dive and lacking in maneuverability.

The Oscar’s primary purpose was to serve as a firing platform for twenty-four enormous P-700 Granit missiles, code-named rather literally SS-N-19 Shipwrecks by NATO. The ten-meter long cruise missiles weigh almost eight tons each, and can be launched from underwater at surface targets nearly four hundred miles away. The missiles boost from their launch tubes using a rocket motor before switching to a ramjet to cruise at speeds as high as Mach 2.5, depending on altitude. They are guided to the target by a satellite system, which the Oscar can link with via an antenna. If multiple Granits are fired in a volley, they can be networked together to relay targeting information and approach from different angles. The Granit missiles can also be equipped with five-hundred-kiloton nuclear warheads.

Although Kirov-class battle cruisers and the aircraft carrier Admiral Kuznetsov can also carry Granit missiles, they are far easier to detect than an Oscar, which can unload its missiles from underwater with far less threat of retaliation.

The Oscar doesn’t lack for shorter-range backup weapons. In addition to its four regular 533-millimeter tubes that can fire RPK-2 “Starfish” anti-submarine missiles, it has two 650-millimeter tubes that can fire extra-large SS-N-16 Stallion missiles, which can strike targets as far as sixty-three miles away. Both rocket-powered missiles can deploy either conventional torpedoes or nuclear depth charges.

The first two Oscars, the Arkhangelsk and Murmansk, were completed in the Severodvinsk shipyards in 1980 and 1982. These were followed by eleven Project 949A Antey boats between 1982 and 1996. These newer and likely stealthier Oscar IIs were ten meters longer, featured updated electronics, and were upgraded from four- to seven-bladed propellers. Construction of three more Oscars was commenced between 1992 and 1994, but then abandoned with the parts diverted to other purposes.

In the post-Soviet era, the Russian Navy concentrated on preserving and updating its Oscar fleet at the expense of its older designs. Oscars continued shadowing U.S. aircraft carriers during the 1990s, and one even became tangled in the nets of Spanish fishing trawler in 1999.

As is true for all but handful of submarines since World War II, the Oscar has thankfully never been used in combat. However, submarine operations remain hazardous even when not being threatened by enemy torpedoes and depth charges.

On August 12, 2000, an explosion, followed by a massive detonation equivalent to three to seven tons of TNT, occurred on board the Kursk while it was submerged participating in a naval exercise off of Severomorsk. Up to twenty-three of the ship’s 118-man crew managed to survive the initial blast in the ninth compartment of the vessel, but rescuers were tragically unable to intervene in time. An investigation concluded that hydrogen peroxide leaking from a poorly welded Type 65 torpedo was the likely source of the first blast, leading to a chain detonation of the other torpedoes. Another theory is that crew error due to lack of training caused the torpedo detonation.

Last year, on April 7, 2015, the Oscar-class Orel caught fire while at dry-dock in Severodvinsk. This time the culprit was insulation between the inner and outer hull that combusted while parts were being welded. Fortunately, the nuclear fuel and weaponry were not on board at the time.

Today, seven or eight Oscar II–class submarines continue to serve in the Russian Navy’s Pacific and Northern fleets. The new, stealthier Yasen-class submarines are intended to eventually replace the Oscars in the anti-carrier role, though only one, the Severodvinsk, has been completed so far.

However, the Russian military has announced it is upgrading at least three—though possibly all—of the remaining Oscars to the Project 949AM model by 2020, supposedly at a cost of $180 million per submarine. The upgrade will replace the old Granit missiles with seventy-two modern Oniks and Klub anti-shipping cruise missiles. Other upgrades would include new sensors, combat information and navigation systems.

The Oscar-class subs are not at the cutting edge of stealthy submarine technology—but they may remain an effective means to threaten valuable surface ships from extremely long range with their cruise missile armament.

Sébastien Roblin holds a Master’s Degree in Conflict Resolution from Georgetown University and served as a university instructor for the Peace Corps in China. He has also worked in education, editing, and refugee resettlement in France and the United States. He currently writes on security and military history for War Is Boring.

Image: Russian submarine Tomsk in Vilyuchinsk. Wikimedia Commons/Sergey Konovalov/Mil.ru