HMS Narcissus (K74)

Aberdeen is a city in North East Scotland, and is the third most populous city in the country. Aberdeen is one of Scotland's 32 local government council areas, and has a 2020 population estimate of 198,590 for the city of Aberdeen, and 227,560 for the local council area making it the United Kingdom's 39th most populous built-up area. The city is 93 mi (150 km) northeast of Edinburgh and 398 mi (641 km) north of London, and is the northernmost major city in the United Kingdom. Aberdeen has a long, sandy coastline and features an oceanic climate, with cool summers and mild, rainy winters.

The Battle of the Atlantic, the longest continuous military campaign in World War II, ran from 1939 to the defeat of Nazi Germany in 1945, covering a major part of the naval history of World War II. At its core was the Allied naval blockade of Germany, announced the day after the declaration of war, and Germany's subsequent counter-blockade. The campaign peaked from mid-1940 through to the end of 1943.

Nazi Germany was the German state between 1933 and 1945, when Adolf Hitler and the Nazi Party controlled the country, transforming it into a dictatorship. Under Hitler's rule, Germany quickly became a totalitarian state where nearly all aspects of life were controlled by the government. The Third Reich, meaning "Third Realm" or "Third Empire", alluded to the Nazi claim that Nazi Germany was the successor to the earlier Holy Roman Empire (800–1806) and German Empire (1871–1918). The Third Reich, which Hitler and the Nazis referred to as the Thousand-Year Reich, ended in May 1945 after just 12 years when the Allies defeated Germany, ending World War II in Europe.

Sonar is a technique that uses sound propagation to navigate, measure distances (ranging), communicate with or detect objects on or under the surface of the water, such as other vessels.

Radar is a radiolocation system that uses radio waves to determine the distance (ranging), angle (azimuth), and radial velocity of objects relative to the site. It is used to detect and track aircraft, ships, spacecraft, guided missiles, and motor vehicles, and map weather formations, and terrain. A radar system consists of a transmitter producing electromagnetic waves in the radio or microwaves domain, a transmitting antenna, a receiving antenna and a receiver and processor to determine properties of the objects. Radio waves from the transmitter reflect off the objects and return to the receiver, giving information about the objects' locations and speeds.

A depth charge is an anti-submarine warfare (ASW) weapon. It is intended to destroy a submarine by being dropped into the water nearby and detonating, subjecting the target to a powerful and destructive hydraulic shock. Most depth charges use high explosive charges and a fuze set to detonate the charge, typically at a specific depth. Depth charges can be dropped by ships, patrol aircraft, and helicopters.

The Hedgehog was a forward-throwing anti-submarine weapon that was used primarily during the Second World War. The device, which was developed by the Royal Navy, fired up to 24 spigot mortars ahead of a ship when attacking a U-boat. It was deployed on convoy escort warships such as destroyers and corvettes to supplement the depth charges.

The Firth of Clyde is the mouth of the River Clyde. It is located on the west coast of Scotland and constitutes the deepest coastal waters in the British Isles. The firth is sheltered from the Atlantic Ocean by the Kintyre peninsula, which encloses the outer firth in Argyll and Ayrshire. The Kilbrannan Sound is a large arm of the Firth of Clyde, separating the Kintyre Peninsula from the Isle of Arran. Within the Firth of Clyde is another major island – the Isle of Bute. Given its strategic location at the entrance to the middle and upper Clyde, Bute played a vital naval military role during World War II.

Greenock is a town and administrative centre in the Inverclyde council area in Scotland, United Kingdom and a former burgh within the historic county of Renfrewshire, located in the west central Lowlands of Scotland. It forms part of a contiguous urban area with Gourock to the west and Port Glasgow to the east.

Govan is a district, parish, and former burgh now part of south-west City of Glasgow, Scotland. It is situated 2.5 miles (4.0 km) west of Glasgow city centre, on the south bank of the River Clyde, opposite the mouth of the River Kelvin and the district of Partick. Historically it was part of the County of Lanark.

Newfoundland was a British dominion in eastern North America, today the modern Canadian province of Newfoundland and Labrador. It was established on 26 September 1907, and confirmed by the Balfour Declaration of 1926 and the Statute of Westminster of 1931. It included the island of Newfoundland, and Labrador on the continental mainland. Newfoundland was one of the original dominions within the meaning of the Balfour Declaration, and accordingly enjoyed a constitutional status equivalent to the other dominions of the time.

The Bay of Biscay, known in Spain as the Gulf of Biscay, and in France and some border regions as the Gulf of Gascony, is a gulf of the northeast Atlantic Ocean located south of the Celtic Sea. It lies along the western coast of France from Point Penmarc'h to the Spanish border, and the northern coast of Spain west to Cape Ortegal. The south area of the Bay of Biscay that washes over the northern coast of Spain is known locally as the Cantabrian Sea.

Gibraltar is a British Overseas Territory and city located at the southern tip of the Iberian Peninsula. It has an area of 6.7 km2 (2.6 sq mi) and is bordered to the north by Spain. The landscape is dominated by the Rock of Gibraltar, at the foot of which is a densely populated town area, home to over 32,000 people, primarily Gibraltarians.

Freetown is the capital and largest city of Sierra Leone. It is a major port city on the Atlantic Ocean and is located in the Western Area of the country. Freetown is Sierra Leone's major urban, economic, financial, cultural, educational and political centre, as it is the seat of the Government of Sierra Leone. The population of Freetown was 1,055,964 at the 2015 census.

The Allies, formally referred to as the United Nations from 1942, were an international military coalition formed during the Second World War (1939–1945) to oppose the Axis powers, led by Nazi Germany, Imperial Japan, and Fascist Italy. Its principal members by the end of 1941 were the United Kingdom, United States, Soviet Union, and China.

In naval terminology, a destroyer is a fast, manoeuvrable, long-endurance warship intended to escort larger vessels in a fleet, convoy, or battle group and defend them against powerful short-range attackers. They were originally developed in 1885 by Fernando Villaamil for the Spanish Navy as a defense against torpedo boats, and by the time of the Russo-Japanese War in 1904, these "torpedo boat destroyers" (TBDs) were "large, swift, and powerfully armed torpedo boats designed to destroy other torpedo boats". Although the term "destroyer" had been used interchangeably with "TBD" and "torpedo boat destroyer" by navies since 1892, the term "torpedo boat destroyer" had been generally shortened to simply "destroyer" by nearly all navies by the First World War.