German submarine U-997

U-boats were naval submarines operated by Germany, particularly in the First and Second World Wars. Although at times they were efficient fleet weapons against enemy naval warships, they were most effectively used in an economic-warfare role and enforcing a naval blockade against enemy shipping. The primary targets of the U-boat campaigns in both wars were the merchant convoys bringing supplies from Canada and other parts of the British Empire, and from the United States, to the United Kingdom and to the Soviet Union and the Allied territories in the Mediterranean. German submarines also targeted Brazilian merchant ships during both World Wars and, twice over, precipitated Brazil's decision to give up its neutral stance and declare war on Germany.

The diesel engine, named after Rudolf Diesel, is an internal combustion engine in which ignition of the fuel is caused by the elevated temperature of the air in the cylinder due to mechanical compression; thus, the diesel engine is called a compression-ignition engine. This contrasts with engines using spark plug-ignition of the air-fuel mixture, such as a petrol engine or a gas engine.

Brown, Boveri & Cie. was a Swiss group of electrical engineering companies. It was founded in Zürich, in 1891 by Charles Eugene Lancelot Brown and Walter Boveri who worked at the Maschinenfabrik Oerlikon. In 1970 BBC took over the Maschinenfabrik Oerlikon. In 1988 it merged with ASEA to form ABB.

A motor–generator is a device for converting electrical power to another form. Motor–generator sets are used to convert frequency, voltage, or phase of power. They may also be used to isolate electrical loads from the electrical power supply line. Large motor–generators were widely used to convert industrial amounts of power while smaller motor–generators were used to convert battery power to higher DC voltages.

A modern torpedo is an underwater ranged weapon launched above or below the water surface, self-propelled towards a target, and with an explosive warhead designed to detonate either on contact with or in proximity to the target. Historically, such a device was called an automotive, automobile, locomotive, or fish torpedo; colloquially a fish. The term torpedo originally applied to a variety of devices, most of which would today be called mines. From about 1900, torpedo has been used strictly to designate a self-propelled underwater explosive device.

German submarine U-1105, a Type VII-C/41 U-boat of Nazi Germany's Kriegsmarine, was built at the Nordseewerke Shipyard, Emden, Germany, and commissioned on 3 June 1944. Oberleutnant zur See Hans-Joachim Schwarz was given command. He would command U-1105 for the remainder of the war.

German submarine U-1172 was a Type VIIC/41 U-boat built for Nazi Germany's Kriegsmarine for service during World War II. She was laid down on 7 June 1943 by Danziger Werft, Danzig as yard number 144, launched on 3 December 1943 and commissioned on 20 April 1944 under Oberleutnant zur See Jürgen Kuhlmann.

German submarine U-1306 was a Type VIIC/41 U-boat of Nazi Germany's Kriegsmarine during World War II.

German submarine U-1307 was a Type VIIC/41 U-boat of Nazi Germany's Kriegsmarine during World War II.

German submarine U-1308 was the last Type VIIC/41 submarine to be laid down, launched and commissioned by Nazi Germany's Kriegsmarine during World War II. The Oberkommando der Marine or OKM,, had decided near the end of World War II to put all of its resources into building newer types of Unterseeboot, such as the types XXI and XXIII. U-1308 was part of a batch of eight U-boats ordered on 1 August 1942 to be built at Flensburger Schiffbau-Gesellschaft, Flensburg. She was laid down on 16 February 1944 and launched on 22 November. The eight boats were commissioned over a 12-month period between February 1944 and 17 January 1945.

German Type XXIII submarines were the first so-called elektroboote to become operational. They were small coastal submarines designed to operate in the shallow waters of the North Sea, Black Sea and Mediterranean Sea, where larger Type XXI electric boats were at risk in World War II. They were so small they could carry only two torpedoes, which had to be loaded externally. As with their far larger sisters—the Type XXI—they were able to remain submerged almost all of the time and were faster than conventional U-boats, due to the improved streamlining of their shape, batteries with larger capacity and the snorkel, which allowed the diesel engines to be used while submerged. The Type XXI and XXIII U-boats revolutionized post-war submarine design. Nearly a thousand Type XXIII boats were projected towards the close of World War II, but most of these were either cancelled, scrapped incomplete, or only projected.

The 5th U-boat Flotilla, also known as Emsmann Flotilla, was a U-boat flotilla of Nazi Germany's Kriegsmarine during World War II.

The 9th U-boat Flotilla was formed in October 1941 in Brest. It became operational in April 1942, after the first combat ready U-boat, U-213, reached the Brest base on 20 March 1942. The flotilla operated mostly various marks of the Type VII U-boat and it concentrated its efforts mainly in the North Atlantic, against convoys to and from Great Britain. The flotilla served from Brest until the base was threatened with being captured by American forces. The last of the flotilla's U-boats, the U-256 left Brest on 4 September 1944 for Bergen, Norway, and this marked the end of the 9th Flotilla. All its surviving boats were reassigned to the 11th U-boat Flotilla in Bergen.

The 13th U-boat Flotilla was a World War II U-boat unit of Nazi Germany's Kriegsmarine stationed in Trondheim, Norway. The emblem of the unit was a cross with a Viking ship in the middle.

The 14th U-boat Flotilla was a short-lived unit of Nazi Germany's Kriegsmarine during World War II.

The geographic coordinate system (GCS) is a spherical or ellipsoidal coordinate system for measuring and communicating positions directly on the Earth as latitude and longitude. It is the simplest, oldest and most widely used of the various spatial reference systems that are in use, and forms the basis for most others. Although latitude and longitude form a coordinate tuple like a cartesian coordinate system, the geographic coordinate system is not cartesian because the measurements are angles and are not on a planar surface.

Operation Deadlight was the code name for the Royal Navy operation of November 1945 – February 1946 to scuttle German U-boats surrendered to the Allies after the defeat of Germany near the end of World War II.

The Soviet Navy was the naval warfare uniform service branch of the Soviet Armed Forces. Often referred to as the Red Fleet, the Soviet Navy made up a large part of the Soviet Union's strategic planning in the event of a conflict with the opposing superpower, the United States, during the Cold War (1945–1991). The Soviet Navy played a large role during the Cold War, either confronting the North Atlantic Treaty Organization in western Europe or power projection to maintain its sphere of influence in eastern Europe.

Norway, officially the Kingdom of Norway, is a Nordic country in Northern Europe, the mainland territory of which comprises the western and northernmost portion of the Scandinavian Peninsula. The remote Arctic island of Jan Mayen and the archipelago of Svalbard also form part of Norway. Bouvet Island, located in the Subantarctic, is a dependency of Norway; it also lays claims to the Antarctic territories of Peter I Island and Queen Maud Land. The capital and largest city in Norway is Oslo.

The Soviet Union, officially the Union of Soviet Socialist Republics (USSR), was a transcontinental country spanning most of northern Eurasia that existed from 30 December 1922 to 26 December 1991. A flagship communist state, it was nominally a federal union of fifteen national republics; in practice, both its government and its economy were highly centralized until its final years. It was a one-party state governed by the Communist Party of the Soviet Union, with the city of Moscow serving as its capital as well as that of its largest and most populous republic: the Russian SFSR. Other major cities included Leningrad, Kiev, Minsk, Tashkent, Alma-Ata, and Novosibirsk. It was the largest country in the world, covering over 22,402,200 square kilometres (8,649,500 sq mi) and spanning eleven time zones.