Northern Fleet in the context of Submarines

A submarine (often shortened to sub) is a watercraft capable of independent operation underwater. (It differs from a submersible, which has more limited underwater capability.) The term "submarine" is also sometimes used historically or informally to refer to remotely operated vehicles and robots, or to medium-sized or smaller vessels (such as the midget submarine and the wet sub). Submarines are referred to as boats rather than ships regardless of their size.

Although experimental submarines had been built earlier, submarine design took off during the 19th century, and submarines were adopted by several navies. They were first used widely during World War I (1914–1918), and are now used in many navies, large and small. Their military uses include: attacking enemy surface ships (merchant and military) or other submarines; aircraft carrier protection; blockade running; nuclear deterrence; stealth operations in denied areas when gathering intelligence and doing reconnaissance; denying or influencing enemy movements; conventional land attacks (for example, launching a cruise missile); and covert insertion of frogmen or special forces. Their civilian uses include: marine science; salvage; exploration; and facility inspection and maintenance. Submarines can be modified for specialized functions such as search-and-rescue missions and undersea cable repair. They are also used in the tourism industry and in undersea archaeology. Modern deep-diving submarines derive from the bathyscaphe, which evolved from the diving bell.

Port of Arkhangelsk (Russian: Архангельский морской торговый порт) is a major seaport at Arkhangelsk, located at the mouth of the Northern Dvina River, 50 kilometres (31 mi) from the Dvina Bay of the White Sea. The important point links with coastal areas of the Russian North. For much of Russia's history this was Russia's main centre of international maritime trade, conducted by the so-called Pomors ("seaside settlers") from Kholmogory.

During the Soviet period it was a major naval and submarine base of the Soviet Navy. It is still a major naval base of the Northern Fleet of the Russian Navy.

The Russian cruiser Marshal Ustinov (Russian: Маршал Устинов), is a Slava-class cruiser (Project 1164) of the Russian Navy. The Russian name for the ship type is Raketnyy Kreyser (RKR), meaning "Missile Cruiser". The ship is named after Dmitriy Ustinov, a former Soviet Minister of Defence. Marshal Ustinov was assigned to the 43rd Missile Ship Division of the Northern Fleet, whose homeport is in Severomorsk. From 2012 to 2016, the cruiser underwent a major overhaul. The vessel returned to service in 2017 and has since been deployed to the Mediterranean Sea.

Kola Bay (Russian: Кольский залив) or Murmansk Fjord is a 57-km-long fjord of the Barents Sea that cuts into the northern part of the Kola Peninsula. It is up to 7 km wide and has a depth of 200 to 300 metres. The Tuloma, Rosta and Kola Rivers discharge into the bay.

The eastern shore is craggy and precipitous, the western one is comparatively level. The ports of Murmansk and Severomorsk sit on the east side. Polyarny, the main base of Russia's Northern Fleet, is on the west side of the bay.