HMCS Thunder (J156)

The Halcyon class was a class of 21 oil-fired minesweepers built for the British Royal Navy between 1933 and 1939. They were given traditional small ship names used historically by the Royal Navy and served during World War II.

The Fundy-class minesweepers were a class of four minesweepers operated by the Royal Canadian Navy during the Second World War. All four ships entered service in 1938 and the class were discarded in 1945, sold for mercantile service. Three ended up sold to Chinese interests, while one remained active in Canada until 1987.

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.

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.

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 draft or draught of a ship's hull is the vertical distance between the waterline and the bottom of the hull (keel). The draught of the vessel is the maximum depth of any part of the vessel, including appendages such as rudders, propellers and drop keels if deployed. Draft determines the minimum depth of water a ship or boat can safely navigate. The related term air draft is the maximum height of any part of the vessel above 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 knot is a unit of speed equal to one nautical mile per hour, exactly 1.852 km/h. The ISO standard symbol for the knot is kn. The same symbol is preferred by the Institute of Electrical and Electronics Engineers (IEEE), while kt is also common, especially in aviation, where it is the form recommended by the International Civil Aviation Organization (ICAO). The knot is a non-SI unit. The knot is used in meteorology, and in maritime and air navigation. A vessel travelling at 1 knot along a meridian travels approximately one minute of geographic latitude in one hour.

Fuel oil is any of various fractions obtained from the distillation of petroleum. Such oils include distillates and residues. Fuel oils include heavy fuel oil, marine fuel oil (MFO), bunker fuel, furnace oil (FO), gas oil (gasoil), heating oils, diesel fuel and others.

The Oerlikon 20 mm cannon is a series of autocannons, based on an original German Becker Type M2 20 mm cannon design that appeared very early in World War I. It was widely produced by Oerlikon Contraves and others, with various models employed by both Allied and Axis forces during World War II. Many versions of the cannon are still used today.

The bridge, also known as the pilothouse or wheelhouse, is a room or platform of a ship from which the ship can be commanded. When a ship is under way, the bridge is manned by an officer of the watch aided usually by an able seaman acting as a lookout. During critical maneuvers the captain will be on the bridge, often supported by an officer of the watch, an able seaman on the wheel and sometimes a pilot, if required.

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 keel is the bottom-most longitudinal structural element on a vessel. On some sailboats, it may have a hydrodynamic and counterbalancing purpose, as well. The laying of the keel is often the initial step in the construction of a ship. In the British and American shipbuilding traditions, this event marks the beginning date of a ships construction.

Ontario is one of the thirteen provinces and territories of Canada. Located in Central Canada, it is Canada's most populous province, with 38.3 percent of the country's population, and is the second-largest province by total area. Ontario is Canada's fourth-largest jurisdiction in total area when the territories of the Northwest Territories and Nunavut are included. It is home to the nation's capital city, Ottawa, and the nation's most populous city, Toronto, which is Ontario's provincial capital.

Halifax is the capital and largest municipality of the Canadian province of Nova Scotia, and the largest municipality in Atlantic Canada. Halifax is one of Canada's fastest growing municipalities, and as of 2022, it is estimated that the CMA population of Halifax was 480,582, with 348,634 people in its urban area. The regional municipality consists of four former municipalities that were amalgamated in 1996: Halifax, Dartmouth, Bedford, and Halifax County.

A convoy is a group of vehicles, typically motor vehicles or ships, traveling together for mutual support and protection. Often, a convoy is organized with armed defensive support and can help maintain cohesion within a unit. It may also be used in a non-military sense, for example when driving through remote areas.

The Azores, officially the Autonomous Region of the Azores, is one of the two autonomous regions of Portugal. It is an archipelago composed of nine volcanic islands in the Macaronesia region of the North Atlantic Ocean, about 1,400 km (870 mi) west of Lisbon, about 1,500 km (930 mi) northwest of Morocco, and about 1,930 km (1,200 mi) southeast of Newfoundland, Canada.

Portland Harbour is located beside the Isle of Portland, Dorset, on the south coast of England. Construction of the harbour began in 1849; when completed in 1872, its 520-hectare (1,300-acre) surface area made it the largest man-made harbour in the world, and remains one of the largest in the world today. It is naturally protected by Portland to the south, Chesil Beach to the west and mainland Dorset to the north. It consists of four breakwaters — two southern and two northern. These have a total length of 4.57 km and enclose approximately 1,000 hectares of water.

The Battle of Cherbourg was part of the Battle of Normandy during World War II. It was fought immediately after the successful Allied landings on 6 June 1944. Allied troops, mainly American, isolated and captured the fortified port, which was considered vital to the campaign in Western Europe, in a hard-fought, month-long campaign.

The bombardment of Cherbourg took place on June 25, 1944, during World War II, when ships from the United States Navy and the British Royal Navy attacked German fortifications in and near the city, firing in support of U.S. Army units that were engaged in the Battle of Cherbourg. In doing so, the Allied naval forces engaged in a series of duels with coastal batteries and provided close support to infantry as they fought to gain control of the city. The bombardment was initially scheduled to last just two hours but it was later extended by an hour to support army units attempting to break into Cherbourg's city streets. After the bombardment, German resistance lasted until June 29, when the port was eventually captured by the Allies. Afterwards, the task of clearing the port for use lasted several weeks.

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.

Plymouth is a port city and unitary authority in South West England. It is located on the south coast of Devon, approximately 36 miles (58 km) south-west of Exeter and 193 miles (311 km) south-west of London. It is bordered by Cornwall to the west and south-west.

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.