Submarine in the context of "Carrier strike group"

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 counterblockade. The campaign peaked from mid-1940 to the end of 1943.

The Battle of the Atlantic pitted U-boats and other warships of the German Kriegsmarine (navy) and aircraft of the Luftwaffe (air force) against the Royal Navy, Royal Canadian Navy, United States Navy, and Allied merchant shipping. Convoys, coming mainly from North America and predominantly going to the United Kingdom and the Soviet Union, were protected for the most part by the British and Canadian navies and air forces. These forces were aided by ships and aircraft of the United States beginning on 13 September 1941. The Germans were joined by submarines of the Italian Regia Marina (royal navy) after Germany's Axis ally Italy entered the war on 10 June 1940.

A navy, naval force, military maritime fleet, war navy, or maritime force is the branch of a state's armed forces principally designated for naval and amphibious warfare; namely, lake-borne, riverine, littoral, or ocean-borne combat operations and related functions. It includes anything conducted by surface ships, amphibious ships, submarines, and seaborne aviation, as well as ancillary support, communications, training, and other fields.

The strategic offensive role of a navy is projection of force into areas beyond a country's shores (for example, to protect sea-lanes, deter or confront piracy, ferry troops, or attack other navies, ports, or shore installations). The strategic defensive purpose of a navy is to frustrate seaborne projection-of-force by enemies. The strategic task of a navy also may incorporate nuclear deterrence by use of submarine-launched ballistic missiles. Naval operations can be broadly divided between riverine and littoral applications (brown-water navy), open-ocean applications (blue-water navy), and something in between (green-water navy), although these distinctions are more about strategic scope than tactical or operational division.

Desalination is a process that removes mineral components from saline water. More generally, desalination is the removal of salts and minerals from a substance. One example is soil desalination. This is important for agriculture. It is possible to desalinate saltwater, especially sea water, to produce water for human consumption or irrigation, producing brine as a by-product. Many seagoing ships and submarines use desalination. Modern interest in desalination mostly focuses on cost-effective provision of fresh water for human use. Along with recycled wastewater, it is one of the few water resources independent of rainfall. As stress on the need for freshwater intensifies globally, desalination has become a key part of strategies for global water security. According to a 2019 review in Science of the Total Environment, around 95 million cubic meters per day of desalinated water is produced worldwide, and the demand for desalinated water is expected to grow significantly to help close the global water supply gap.

Due to its energy consumption, desalinating sea water is generally more costly than fresh water from surface water or groundwater, water recycling and water conservation; however, these alternatives are not always available and depletion of reserves is a critical problem worldwide. Desalination processes are using either thermal methods (in the case of distillation) or membrane-based methods (e.g. in the case of reverse osmosis).

A ship's wheel or boat's wheel is a device used aboard a ship, boat, submarine, or airship, with which a helmsman steers the vessel and controls its course. Together with the rest of the steering mechanism, it forms part of the helm (the term helm can mean the wheel alone, or the entire mechanism by which the rudder is controlled). It is connected to a mechanical, electric servo, or hydraulic system which alters the horizontal angle of the vessel's rudder relative to its hull. In some modern ships the wheel is replaced with a simple toggle that remotely controls an electro-mechanical or electro-hydraulic drive for the rudder, with a rudder position indicator presenting feedback to the helmsman.

Marine propulsion is the mechanism or system used to generate thrust to move a watercraft through water. While paddles and sails are still used on some smaller boats, most modern ships are propelled by mechanical systems consisting of an electric motor or internal combustion engine driving a propeller, or less frequently, in pump-jets, an impeller. Marine engineering is the discipline concerned with the engineering design process of marine propulsion systems.

Human-powered paddles and oars, and later, sails were the first forms of marine propulsion. Rowed galleys, some equipped with sail, played an important early role in early human seafaring and warfare. The first advanced mechanical means of marine propulsion was the marine steam engine, introduced in the early 19th century. During the 20th century it was replaced by two-stroke or four-stroke diesel engines, outboard motors, and gas turbine engines on faster ships. Marine nuclear reactors, which appeared in the 1950s, produce steam to propel warships and icebreakers; commercial application, attempted late that decade, failed to catch on. Electric motors using battery packs have been used for propulsion on submarines and electric boats and have been proposed for energy-efficient propulsion.

A hull is the watertight body of a ship, boat, submarine, or flying boat. The hull may open at the top (such as a dinghy), or it may be fully or partially covered with a deck. Atop the deck may be a deckhouse and other superstructures, such as a funnel, derrick, or mast. The line where the hull meets the water surface is called the waterline.

Anti-aircraft warfare (AAW) or air defence (or air defense in American English) is the counter to aerial warfare and includes "all measures designed to nullify or reduce the effectiveness of hostile air action". It encompasses surface-based, subsurface (submarine-launched), and air-based weapon systems, in addition to associated sensor systems, command and control arrangements, and passive measures (e.g. barrage balloons). 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. Missile defence is an extension of air defence, as are initiatives to adapt air defence to the task of intercepting any projectile in flight.

Most modern anti-aircraft (AA) weapons systems are optimised for short-, medium-, or long-range air defence, although some systems may incorporate multiple weapons (such as both autocannons and surface-to-air missiles). 'Layered air defence' usually refers to multiple 'tiers' of air defence systems which, when combined, an airborne threat must penetrate to reach its target; this defence is usually accomplished via the combined use of systems optimised for either short-, medium-, or long-range air defence.

U-boats are naval submarines operated by Germany, especially during World War I and World War II. The term is an anglicized form of the German word U-Boot [ˈuːboːt] , a shortening of Unterseeboot (lit. 'under-sea boat'). Austro-Hungarian Navy submarines were also known as U-boats.

U-boats are especially known for their use in unrestricted submarine warfare in both world wars, attempting to disrupt merchant traffic towards the UK and force the UK out of the war. In World War I, Germany intermittently waged unrestricted submarine warfare against the UK: a first campaign in 1915 was abandoned after strong protests from the US but in February 1917 the Germans, facing deadlock on the continent, saw no other option than to resume the campaign. The renewed campaign failed to achieve its goal mainly because of the introduction of convoys. Instead the campaign ensured final defeat as the campaign was a contributing factor to the entry of the US in the First World War.

The Kriegsmarine (German pronunciation: [ˈkʁiːksmaˌʁiːnə], lit. 'War Navy') was the navy of Nazi Germany from 1935 to 1945. It superseded the Imperial German Navy of the German Empire (1871–1918) and the inter-war Reichsmarine (1919–1935) of the Weimar Republic. The Kriegsmarine was one of three official branches, along with the Heer and the Luftwaffe, of the Wehrmacht, the German armed forces from 1935 to 1945.

In violation of the Treaty of Versailles, the Kriegsmarine grew rapidly during the German naval rearmament in the 1930s. The 1919 treaty had limited the size of the German navy and prohibited the building of submarines.

The Royal Canadian Navy (RCN; French: Marine royale canadienne, MRC) is the naval force of Canada. The navy is one of three environmental commands within the Canadian Armed Forces. As of February 2024, the RCN operates 12 Halifax-class frigates, 4 Kingston-class coastal defence vessels, 4 Victoria-class submarines, 5 Harry DeWolf-class offshore patrol vessels, 8 Orca-class patrol vessels, and several auxiliary vessels. Officially, the RCN consisted of 8,400 Regular Force and 4,100 Primary Reserve sailors, supported by 3,800 civilians.

Founded in 1910 as the Naval Service of Canada (French: Service naval du Canada) and given royal sanction on 29 August 1911, the RCN was amalgamated with the Royal Canadian Air Force and the Canadian Army to form the unified Canadian Armed Forces in 1968, after which it was known as Maritime Command (French: Commandement maritime) until 2011.