J-, K- and N-class destroyer

Anti-aircraft warfare, counter-air or air defence forces is the battlespace response to aerial warfare, defined by NATO as "all measures designed to nullify or reduce the effectiveness of hostile air action". It includes surface based, subsurface, and air-based weapon systems, associated sensor systems, command and control arrangements, and passive measures. It may be used to protect naval, ground, and air forces in any location. However, for most countries, the main effort has tended to be homeland defence. NATO refers to airborne air defence as counter-air and naval air defence as anti-aircraft warfare. Missile defence is an extension of air defence, as are initiatives to adapt air defence to the task of intercepting any projectile in flight.

The E and F-class destroyers were a group of 18 destroyers built for the Royal Navy during the 1930s. The ships were initially assigned to the Home Fleet, although they reinforced the Mediterranean Fleet during the Italian invasion of Abyssinia of 1935–36 and enforced the Non-Intervention Agreement during the Spanish Civil War of 1936–1939. After the beginning of the Second World War in August 1939, the E-class ships were mostly assigned to escort duties under the Western Approaches Command, while the Fs were assigned to escort the ships of the Home Fleet. Between them they sank four German submarines through March 1940 while losing only one ship to a submarine.

The S and T class was a class of sixteen destroyers of the Royal Navy launched in 1942–1943. They were built as two flotillas, known as the 5th and 6th Emergency Flotilla, and they served as fleet and convoy escorts in World War II.

The O and P class was a class of destroyers of the British Royal Navy. Ordered in 1939, they were the first ships in the War Emergency Programme, also known as the 1st and 2nd Emergency Flotilla, respectively. They served as convoy escorts in World War II, and some were subsequently converted to fast second-rate anti-submarine frigates in the 1950s.

The C class was a class of 32 destroyers of the Royal Navy that were launched from 1943 to 1945. The class was built in four flotillas of 8 vessels, the "Ca", "Ch", "Co" and "Cr" groups or sub-classes, ordered as the 11th, 12th, 13th and 14th Emergency Flotillas respectively. The sub-class names are derived from the initial 2 letters of the member ships' names, although the "Ca" class were originally ordered with a heterogeneous mix of traditional destroyer names. A fifth flotilla, the "Ce" or 15th Emergency Flotilla, was planned but were cancelled in favour of the Weapon-class destroyers after only the first two ships had been ordered. The pennant numbers were all altered from "R" superior to "D" superior at the close of World War II; this involved some renumbering to avoid duplications.

The 4.7 inch QF Mark IX and Mark XII were 45-calibre, 4.7-inch (120 mm) naval guns which armed the majority of Royal Navy and Commonwealth destroyers in World War II, and were exported to many countries after World War II as the destroyers they were mounted on were sold off.

The 2-pounder gun, officially the QF 2-pounder and universally known as the pom-pom, was a 40 mm (1.6 in) British autocannon, used as an anti-aircraft gun by the Royal Navy. The name came from the sound that the original models make when firing. This QF 2-pounder was not the same gun as the Ordnance QF 2-pounder, used by the British Army as an anti-tank gun and a tank gun, although they both fired 2 lb (0.91 kg), 40 mm (1.6 in) projectiles.

The Vickers .50 machine gun, also known as the 'Vickers .50' was similar to the .303 inches (7.70 mm) Vickers machine gun but enlarged to use a larger-calibre 0.5-inch (12.7 mm) round. It saw some use in tanks and other fighting vehicles but was more commonly used as a close-in anti-aircraft weapon on Royal Navy and Allied ships, typically in a four-gun mounting (UK) or two-gun mounting (Dutch). The Vickers fired British .50 Vickers (12.7×81mm) ammunition, not the better known American .50 BMG (12.7×99mm).

A coincidence rangefinder or coincidence telemeter is a type of rangefinder that uses mechanical and optical principles to allow an operator to determine the distance to a visible object. There are subtypes split-image telemeter, inverted image, or double-image telemeter with different principles how two images in a single ocular are compared. Coincidence rangefinders were important elements of fire control systems for long-range naval guns and land-based coastal artillery circa 1890–1960. They were also used in rangefinder cameras.

The Fuze Keeping Clock (FKC) was a simplified version of the Royal Navy's High Angle Control System analogue fire control computer. It first appeared as the FKC MkII in destroyers of the 1938 Tribal class, while later variants were used on sloops, frigates, destroyers, aircraft carriers and several cruisers. The FKC MkII was a non-tachymetric anti-aircraft fire control computer. It could accurately engage targets with a maximum speed of 250 knots.

The L and M class was a class of sixteen destroyers which served in the British Royal Navy during World War II. The ships of the class were launched between 1939 and 1942.

The quarterdeck is a raised deck behind the main mast of a sailing ship. Traditionally it was where the captain commanded his vessel and where the ship's colours were kept. This led to its use as the main ceremonial and reception area on board, and the word is still used to refer to such an area on a ship or even in naval establishments on land. Many such facilities have areas decorated like shipboard quarterdecks.

The QF 4 inch Mk V gun was a Royal Navy gun of World War I which was adapted on HA mountings to the heavy anti-aircraft role both at sea and on land, and was also used as a coast defence gun.

A minesweeper is a small warship designed to remove or detonate naval mines. Using various mechanisms intended to counter the threat posed by naval mines, minesweepers keep waterways clear for safe shipping.

The Type 291 radar was designed as a search radar for ships destroyer-sized and smaller in 1942. By the end of the Second World War it had been installed in almost every British and Commonwealth destroyer and escort ship as well as many submarines, naval trawlers, and motor torpedo boats. Some sets were furnished to the Soviet Union for their destroyers as a part of Lend-Lease.

The Type 271 was a surface search radar used by the Royal Navy and allies during World War II. The first widely used naval microwave-frequency system, it was equipped with an antenna small enough to allow it to be mounted on small ships like corvettes and frigates, while its improved resolution over earlier radars allowed it to pick up a surfaced U-boat at around 3 miles (4.8 km) and its periscope alone at 900 yards (820 m).

The Type 293 radar was designed as a short-range aerial-search radar for surface ships in 1945. It used the same transmitter as the Type 277 surface-search radar, but used a new antenna design intended to cover the area above the ship to provide air warning instead of surface search. The stabilised "cheese" antenna, 6 feet (1.8 m) diameter in the AUR antenna, was upgraded to 8 feet (2.4 m) in Type 293P and to 12 feet (3.7 m) in the postwar Type 293Q.

Ceremonial ship launching involves the performance of ceremonies associated with the process of transferring a vessel to the water. It is a nautical tradition in many cultures, dating back thousands of years, to accompany the physical process with ceremonies which have been observed as public celebration and a solemn blessing, usually but not always, in association with the launch itself.

Hebburn is a town in the metropolitan county of Tyne and Wear, England. It governed under the borough of South Tyneside; formerly governed under the county of Durham until 1974 with its own urban district from 1894 until 1974. It is on the south bank of the River Tyne between Gateshead and Jarrow and opposite Wallsend and Walker.

HMS Jackal was a J-class destroyer of the Royal Navy. Completed in 1939, Jackal served in the Norwegian campaign and the Dunkirk evacuation before being deployed to the Mediterranean in 1941. Jackal took part in the Battle of Crete, and was scuttled after being heavily damaged by German bombers on 12 May 1942.

John Brown and Company of Clydebank was a Scottish marine engineering and shipbuilding firm. It built many notable and world-famous ships including RMS Lusitania, RMS Aquitania, HMS Hood, HMS Repulse, RMS Queen Mary, RMS Queen Elizabeth and the Queen Elizabeth 2.

Clydebank is a town in West Dunbartonshire, Scotland. Situated on the north bank of the River Clyde, it borders the village of Old Kilpatrick to the west, and the Yoker and Drumchapel areas of the adjacent City of Glasgow immediately to the east. Depending on the definition of the town's boundaries, the suburban areas of Duntocher, Faifley and Hardgate either surround Clydebank to the north, or are its northern outskirts, with the Kilpatrick Hills beyond.

HMS Jaguar was a J-class destroyer of the Royal Navy. Commissioned in September 1939, she was present at the Dunkirk evacuation the following year, during which Jaguar was damaged by dive bombers. She later served in the Mediterranean and was involved in several actions there. She was torpedoed off the coast of Egypt on 26 March 1942 and sunk.

Dumbarton is a town in West Dunbartonshire, Scotland, on the north bank of the River Clyde where the River Leven flows into the Clyde estuary. In 2006, it had an estimated population of 19,990.

HMS Juno was a J-class destroyer of the Royal Navy laid down by the Fairfield Shipbuilding and Engineering Company, Limited, at Govan in Scotland on 5 October 1937, launched on 8 December 1938 and commissioned on 25 August 1939. Juno participated in the Battle of Calabria in July 1940 and the Battle of Cape Matapan in March 1941.

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.

HMS Janus, named after the Roman god, was a Javelin or J-class destroyer of the Royal Navy. She was ordered from the Swan Hunter & Wigham Richardson Limited at Wallsend-on-Tyne as part of the 1936 Build Programme and laid down on 29 September 1937, launched on 10 November 1938 and commissioned on 5 August 1939.

HMS Javelin was a J-class destroyer of the Royal Navy.