Navy
First at Taranto in 1940 and then at Pearl Harbor in 1941, the carrier demonstrated its ability to strike decisively at enemy ships out of sight and range of surface vessels. The Battle of Leyte Gulf (1944) was arguably the largest naval battle in history; it was also the last battle in which battleships played a significant role. By the end of World War II, the carrier had become the dominant force of naval warfare.
World War II also saw the United States become by far the largest naval power in the world. In the late 20th and early 21st centuries, the United States Navy possessed over 70% of the world's total numbers and total tonnage of naval vessels of 1,000 tons or greater. Throughout the rest of the 20th century, the United States Navy would maintain a tonnage greater than that of the next 17 largest navies combined. During the Cold War, the Soviet Navy became a significant armed force, with large numbers of large, heavily armed ballistic missile submarines and extensive use of heavy, long-ranged antisurface missiles to counter the numerous United States carrier battle groups. Only two nations, the United States and France, presently operate CATOBAR carriers of any size, while Russia, China and India operate sizeable STOBAR carriers (although all three are originally of Russian design). The United Kingdom is also operating two Queen Elizabeth-class carriers, which are the largest STOVL vessels in service, and India is currently building one aircraft carrier, INS Vikrant, and considering another. France is also looking at a new carrier, probably using a CATOBAR system and possibly based on the British Queen Elizabeth design.

Operations: A navy typically operates from one or more naval bases. The base is a port that is specialized in naval operations, and often includes housing, a munitions depot, docks for the vessels, and various repair facilities. During times of war temporary bases may be constructed in closer proximity to strategic locations, as it is advantageous in terms of patrols and station-keeping. Nations with historically strong naval forces have found it advantageous to obtain basing rights in other countries in areas of strategic interest.
Navy ships can operate independently or with a group, which may be a small squadron of comparable ships, or a larger naval fleet of various specialized ships. The commander of a fleet travels in the flagship, which is usually the most powerful vessel in the group. Before radio was invented, commands from the flagship were communicated by means of flags. At night signal lamps could be used for a similar purpose. Later these were replaced by the radio transmitter, or the flashing light when radio silence was needed.
A "blue water navy" is designed to operate far from the coastal waters of its home nation. These are ships capable of maintaining station for long periods of time in deep ocean, and will have a long logistical tail for their support. Many are also nuclear powered to save having to refuel. By contrast a "brown water navy" operates in the coastal periphery and along inland waterways, where larger ocean-going naval vessels can not readily enter. Regional powers may maintain a "green water navy" as a means of localized force projection. Blue water fleets may require specialized vessels, such as minesweepers, when operating in the littoral regions along the coast.

Traditions: A basic tradition is that all ships commissioned in a navy are referred to as ships rather than vessels, with the exception of destroyers and submarines, which are known as boats. The prefix on a ship's name indicates that it is a commissioned ship.An important tradition on board naval vessels of some nations has been the ship's bell. This was historically used to mark the passage of time, as warning devices in heavy fog, and for alarms and ceremonies.
The ship's captain, and more senior officers are "piped" aboard the ship using a Boatswain's call.
In the United States, the First Navy Jack is a flag that has the words, "Don't Tread on Me" on the flag.
By English tradition, ships have been referred to as a "she". However, it was long considered bad luck to permit women to sail on board naval vessels. To do so would invite a terrible storm that would wreck the ship. The only women that were welcomed on board were figureheads mounted on the prow of the ship.
Firing a cannon salute partially disarms the ship, so firing a cannon for no combat reason showed respect and trust. As the tradition evolved, the number of cannon fired became an indication of the rank of the official being saluted.

Naval organization: 

Ships: Historically, navy ships were primarily intended for warfare. They were designed to withstand damage and to inflict the same, but only carried munitions and supplies for the voyage (rather than merchant cargo). Often, other ships which were not built specifically for warfare, such as the galleon or the armed merchant ships in World War II, did carry armaments. In more recent times, navy ships have become more specialized and have included supply ships, troop transports, repair ships, oil tankers and other logistics support ships as well as combat ships.
Modern navy combat ships are generally divided into seven main categories: aircraft carriers, cruisers, destroyers, frigates, corvettes, submarines, and amphibious assault ships. There are also support and auxiliary ships, including the oiler, minesweeper, patrol boat, hydrographic and oceanographic survey ship and tender. During the age of sail, the ship categories were divided into the ship of the line, frigate, and sloop-of-war.
Naval ship names are typically prefixed by an abbreviation indicating the national navy in which they serve. For a list of the prefixes used with ship names (HMS, USS, LÉ, etc.) see ship prefix.
Today's warships are significantly faster than in years past, thanks to much improved propulsion systems. Also, the efficiency of the engines has improved, in terms of fuel, and of how many sailors it takes to operate them. In World War II, ships needed to refuel very often. However, today ships can go on very long journeys without refueling. Also, in World War II, the engine room needed about a dozen sailors to work the many engines, however, today, only about 4–5 are needed (depending on the class of the ship). Today, naval strike groups on longer missions are always followed by a range of support and replenishment ships supplying them with anything from fuel and munitions, to medical treatment and postal services. This allows strike groups and combat ships to remain at sea for several months at a time.

Boats: The term "boat" refers to small craft limited in their use by size and usually not capable of making lengthy independent voyages at sea. The old navy adage to differentiate between ships and boats is that boats are capable of being carried by ships. (Submarines by this rule are ships rather than boats, but are customarily referred to as boats reflecting their previous smaller size.)
Navies use many types of boat, ranging from 9-foot (2.7 m) dinghies to 135-foot (41 m) landing craft. They are powered by either diesel engines, out-board gasoline engines, or waterjets. Most boats are built of aluminum, fiberglass, or steel. Rigid-hulled inflatable boats are also used.
Patrol boats are used for patrols of coastal areas, lakes and large rivers.

Landing craft are designed to carry troops, vehicles, or cargo from ship to shore under combat conditions, to unload, to withdraw from the beach, and to return to the ship. They are rugged, with powerful engines, and usually armed. There are many types in today's navies including hovercraft. They will typically have a power-operated bow ramp, a cargo well and after structures that house engine rooms, pilot houses, and stowage compartments. These boats are sometimes carried by larger ships.
Special operations craft are high-speed craft used for insertion and extraction of special forces personnel and some may be transportable (and deployed) by air.
Boats used in non-combat roles include lifeboats, mail boats, line handling boats, buoy boats, aircraft rescue boats, torpedo retrievers, explosive ordnance disposal craft, utility boats, dive boats, targets, and work boats. Boats are also used for survey work, tending divers, and minesweeping operations. Boats for carrying cargo and personnel are sometimes known as launches, gigs, barges or shore party boats.

Units: Naval forces are typically arranged into units based on the number of ships included, a single ship being the smallest operational unit. Ships may be combined into squadrons or flotillas, which may be formed into fleets. The largest unit size may be the whole Navy or Admiralty.
A task force can be assembled using ships from different fleets for an operational task.

Personnel: Despite their acceptance in many areas of naval service, female sailors were not permitted to serve on board U.S. submarines until the U.S. Navy lifted the ban in April 2010. The major reasons historically cited by the U.S. Navy were the extended duty tours and close conditions which afford almost no privacy. The United Kingdom's Royal Navy has had similar restrictions. Australia, Canada, Norway, and Spain previously opened submarine service to women sailors.

Ranks: A navy will typically have two sets of ranks, one for enlisted personnel and one for officers.