HMS Delphinium (K77)

Length overall is the maximum length of a vessel's hull measured parallel to the waterline. This length is important while docking the ship. It is the most commonly used way of expressing the size of a ship, and is also used for calculating the cost of a marina berth.

Length between perpendiculars is the length of a ship along the summer load line from the forward surface of the stem, or main bow perpendicular member, to the after surface of the sternpost, or main stern perpendicular member. When there is no sternpost, the centerline axis of the rudder stock is used as the aft end of the length between perpendiculars.

The beam of a ship is its width at its widest point. The maximum beam (BMAX) is the distance between planes passing through the outer extremities of the ship, beam of the hull (BH) only includes permanently fixed parts of the hull, and beam at waterline (BWL) is the maximum width where the hull intersects the surface of the water.

The displacement or displacement tonnage of a ship is its weight. As the term indicates, it is measured indirectly, using Archimedes' principle, by first calculating the volume of water displaced by the ship, then converting that value into weight. Traditionally, various measurement rules have been in use, giving various measures in long tons. Today, tonnes are more commonly used.

The BL 4-inch Mk IX naval gun was a British medium-velocity naval gun introduced in 1917 as secondary armament on the Renown-class battlecruisers and Glorious-class "large light cruisers", but which served most notably as the main armament on Flower-class corvettes throughout World War II.

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 Lewis gun is a First World War–era light machine gun. Designed privately in the United States though not adopted there, the design was finalised and mass-produced in the United Kingdom, and widely used by troops of the British Empire during the war. It had a distinctive barrel cooling shroud and top-mounted pan magazine. The Lewis served to the end of the Korean War, and was widely used as an aircraft machine gun during both World Wars, almost always with the cooling shroud removed, as air flow during flight offers sufficient cooling.

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).

Laying the keel or laying down is the formal recognition of the start of a ship's construction. It is often marked with a ceremony attended by dignitaries from the shipbuilding company and the ultimate owners of the ship.

Henry Robb, Limited, known colloquially as Robbs, was a Scottish shipbuilding company based at Leith Docks in Edinburgh. Robbs was notable for building small-to-medium sized vessels, particularly tugs and dredgers.

Leith is a port area in the north of the city of Edinburgh, Scotland, founded at the mouth of the Water of Leith.

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.

Warship Weeks were British National savings campaigns during the Second World War, with the aim of a Royal Navy warship being adopted by a civil community. During the early parts of the war, the Royal Navy not only had lost many capital ships but was facing increasing pressure to provide escorts for convoys in the Atlantic. While there was not a shortage of sailors, ships sunk by enemy action had to be replaced.

The Eighth Army was a field army of the British Army during the Second World War. It was initially formed as the Western Army on 10 September 1941, in Egypt, before being renamed the Army of the Nile, and finally the Eighth Army on 26 September. It was created to better control the growing Allied forces based in Egypt and to direct their efforts to lift the siege of Tobruk via Operation Crusader.

Tobruk or Tobruck is a port city on Libya's eastern Mediterranean coast, near the border with Egypt. It is the capital of the Butnan District and has a population of 120,000.

HMS Hero was an H-class destroyer built for the Royal Navy in the mid-1930s. During the Spanish Civil War of 1936–1939 the ship enforced the arms blockade imposed by Britain and France on both sides as part of the Mediterranean Fleet. During the first few months of World War II, Hero searched for German commerce raiders in the Atlantic Ocean and participated in the Second Battle of Narvik during the Norwegian Campaign of April–June 1940 before she was transferred to the Mediterranean Fleet in May where she escorted a number of convoys to Malta. The ship took part in the Battle of Cape Spada in July 1940, Operation Abstention in February 1941, and the evacuations of Greece and Crete in April–May 1941.

Operation Vigorous was a British operation during the Second World War, to escort supply convoy MW11 from the eastern Mediterranean to Malta, which took place from 11 to 16 June 1942. Vigorous was part of Operation Julius, a simultaneous operation with Operation Harpoon from Gibraltar and supporting operations. Sub-convoy MW11c sailed from Port Said (Egypt) on 11 June, to tempt the Italian battlefleet to sail early, use up fuel and be exposed to submarine and air attack. MW11a and MW11b sailed next day from Haifa, Port Said and Alexandria; one ship was sent back because of defects. Italian and German (Axis) aircraft attacked MW11c on 12 June and a damaged ship was diverted to Tobruk, just east of Gazala. The merchant ships and escorts rendezvoused on 13 June. The British plans were revealed unwittingly to the Axis by the US Military Attaché in Egypt, Colonel Bonner Fellers, who reported to Washington, D.C. in "Black"-coded wireless messages; it was later discovered that the Black Code had been broken by the Servizio Informazioni Militare.

HMT Islay (T172) was a British Royal Navy Isles-class armed trawler of the Second World War.

German submarine U-81 was a Type VIIC U-boat of the navy (Kriegsmarine) of Nazi Germany during World War II, famous for sinking the aircraft carrier HMS Ark Royal.

The Allied invasion of Sicily, also known as the Battle of Sicily and Operation Husky, was a major campaign of World War II in which the Allied forces invaded the island of Sicily in July 1943 and took it from the Axis powers. It began with a large amphibious and airborne operation, followed by a six-week land campaign, and initiated the Italian campaign.