Understanding the U.S. Navy: Structure and Mission

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The U.S. Navy’s job under federal law is to be ready for prompt, sustained combat at sea and, in peacetime, to promote the nation’s security and prosperity. Its warships rely on a fleet behind the fleet. Supply ships carry fuel, food and equipment to vessels at sea, and tankers can refuel those supply ships so the deliveries can continue.

A deployment also depends on who commands the force, how its fleets are organized, what its ships and aircraft can do, and the people and shipyards that keep them ready. In fiscal years 2016 through 2025, the Navy’s attack submarines lost more than 15,000 operational days to maintenance delays and idle time spent waiting at the pier, the Government Accountability Office found.

What the Navy is built to do

The Navy includes combat forces, service forces and naval aviation. Those forces have several jobs.

Sea control means having freedom to use a particular sea area for a particular period and, when necessary, denying or limiting an enemy’s use of it. That control includes the airspace above the sea and the waters and seabed below it.

Power projection is the ability to strike from the sea, including attacks, amphibious operations and naval special warfare. Naval doctrine describes this as a way to project power ashore without depending on ports or airfields in the area of an operation. Amphibious ships carry forces and supplies and land them from the sea. Naval special warfare includes specially trained small-boat crews that carry special operators and conduct reconnaissance or direct-action missions.

Deterrence seeks to prevent aggression by making an adversary believe the cost of acting would outweigh the benefit. Naval forces also conduct maritime security operations, work with foreign partners, respond to humanitarian disasters and help people leave threatened areas.

These functions overlap: the same force can be prepared for combat and also support security or humanitarian missions.

Who prepares the force and who commands it

The Department of the Navy includes both the Navy and the Marine Corps, including their operating forces, aviation and reserves. Its civilian head, the secretary of the Navy, is appointed by the president with the Senate’s advice and consent.

Under the secretary of defense’s authority, the Navy secretary is responsible for recruiting, organizing, supplying, equipping and training the department’s forces. The job also covers maintenance and the construction and repair of military equipment and facilities.

Naval doctrine separates two kinds of responsibility: administrative, meaning organizing, training and equipping forces, and operational, meaning carrying out military missions. Combatant commanders are military leaders who employ assigned forces for regional or functional missions. They exercise command authority over those forces through service component commanders. A Navy component command is thus the connection between naval forces and the broader military command employing them.

The Chief of Naval Operations (CNO) is an admiral who is directly responsible to the Navy secretary and, within the department, takes precedence over all other officers of the naval service. The CNO advises the secretary on plans, carries approved plans into effect and supervises forces consistently with the authority assigned to combatant commanders.

The CNO also serves as a member of the Joint Chiefs of Staff. As a Joint Chiefs member, the CNO provides military advice; the Joint Chiefs themselves have no executive authority to command combatant forces.

The Coast Guard is a separate case: it normally operates in the Department of Homeland Security. It operates as a service in the Navy when Congress directs that transfer in a declaration of war or when the president directs it. It remains there until the president transfers it back by executive order, and while serving in the Navy it is subject to the Navy secretary’s orders.

What numbered fleets actually organize

The word fleet can obscure the difference between a headquarters and the ships assigned to a mission. A numbered fleet is an operational Navy formation under a naval component commander, organized into task forces and smaller units. Naval task organization divides a fleet into task forces for specified work, task groups within those forces and task units within the groups.

The Navy numbers its fleets, and the numbers identify commands with different responsibilities; they do not describe a single uniform package of ships. Some concentrate on regions, while Tenth Fleet, the Navy’s cyber command, works worldwide.

For example, U.S. Naval Forces Southern Command/U.S. Fourth Fleet serves as the Navy component command for U.S. Southern Command, a geographic combatant command. The combined name identifies both the wider military command and the naval organization serving it.

How ships and aircraft become a fighting force

Aircraft carriers support power projection, forward presence, deterrence, sea control, maritime security and humanitarian assistance. A carrier strike group combines a carrier and the aircraft units aboard it with other surface warships, supply support and sometimes an attack submarine. Its composition varies with the mission.

Guided-missile destroyers are multi-mission surface combatants for warfare against aircraft, submarines and surface ships. They can operate independently or support carrier, expeditionary and surface strike groups.

Attack submarines hunt enemy submarines and surface ships, strike targets ashore with Tomahawk cruise missiles and support special operations forces. Their missions also include intelligence gathering, surveillance, reconnaissance and mine warfare.

Ballistic missile submarines have a different purpose: strategic deterrence through a survivable nuclear strike capability.

Guided-missile submarines serve conventional land-attack and special operations missions. Ohio-class submarines were built as nuclear-powered ballistic-missile submarines. A Nuclear Posture Review is a policy document about U.S. nuclear weapons and their roles. After the 1994 Nuclear Posture Review determined that the nation needed only 14 ballistic missile submarines, four Ohio-class submarines were converted for those missions.

Amphibious transport docks carry Marines, equipment and supplies and land them using landing craft, amphibious vehicles, helicopters or vertical-takeoff aircraft. An amphibious ready group typically combines a large amphibious assault ship with smaller amphibious ships and embarks a Marine Expeditionary Unit with its aircraft, equipment and supplies. The Navy provides the ships, and the Marines they carry provide the force that goes ashore.

The F/A-18E/F Super Hornet is an all-weather fighter and attack aircraft supporting the carrier strike group. The Hawkeye, an airborne early warning aircraft, helps coordinate operations for the carrier group and the joint force, meaning forces from multiple military services. Its long-range radar and communications help detect threats beyond the sensor range of other friendly units.

The P-8A Poseidon performs maritime patrol and reconnaissance, including anti-submarine and anti-surface warfare. MH-60R helicopters operate from ships and carrier squadrons, conducting anti-submarine and anti-surface warfare as well as search and rescue, replenishment and other support missions.

The people behind the platforms

Navy officers command and lead sailors and manage the effective operation of naval assets. The Navy uses rate for an enlisted sailor’s pay grade and rating for an occupational specialty. Officer pay grade is described by rank. Ratings include specialties such as boatswain’s mate, fire controlman and gas turbine systems technician. Two sailors at the same pay grade can consequently have different occupational responsibilities.

The enlisted progression runs from seaman recruit at E-1 through seaman apprentice at E-2 and seaman at E-3. Petty officers third, second and first class occupy E-4, E-5 and E-6; chief, senior chief and master chief petty officers occupy E-7, E-8 and E-9. Chief petty officers bring technical expertise and experience to training both enlisted and officer teams.

Commissioned officer ranks run from ensign (O-1), lieutenant junior grade (O-2) and lieutenant (O-3) through lieutenant commander (O-4), commander (O-5) and captain (O-6). The admiral grades are rear admiral, lower half (O-7), rear admiral (O-8), vice admiral (O-9) and admiral (O-10).

Navy Enlisted Classification codes document specialized training and skills, including submarine maintenance specialties such as refrigeration, hydraulic, valve and pump repair.

Navy Reserve sailors support naval missions in peace and war through supply and transport work, repairs, aviation support, intelligence and cyber operations.

Civilian scientists and engineers also form part of the technical workforce: the Naval Undersea Warfare Center’s Newport division identified most of its full-time civilian staff as scientists or engineers in its fiscal 2023 report.

What keeps a deployed fleet working

Military Sealift Command supplies ships at sea with fuel, food, equipment and other materials through replenishment oilers and dry cargo and ammunition ships. Before the 2026 Rim of the Pacific exercise, the command said a chartered tanker would refuel its logistics ships at sea so they could keep supporting participants without delay.

Navy Installations Command manages shore installations and keeps ports, airfields and training ranges ready for the operating forces. Its responsibilities also include facilities for manning, training and equipping the force and services supporting military families.

Naval doctrine describes maintenance, individual and unit training, and exercises as the combined work needed to create and sustain combat-ready units. Being able to leave port is not the same as being prepared to perform an assigned wartime mission.

Why a larger fleet takes more than a plan

The Constitution gives Congress the power to provide and maintain a Navy and to regulate naval forces. It also requires Treasury spending to follow appropriations made by law. A Navy shipbuilding plan is therefore a proposal until Congress funds it, and a funded ship still has to be built.

Federal law requires at least 11 operational aircraft carriers and at least 31 operational amphibious warfare ships, including at least 10 amphibious assault ships. For that legal minimum, operational includes ships temporarily unavailable for worldwide deployment because of routine or scheduled maintenance or repair. Meeting that definition does not establish that every counted ship is immediately available for a mission.

The Navy’s fiscal-year 2027 shipbuilding plan lays out a larger, more capable fleet, which the acting Navy secretary called the Golden Fleet. The plan prioritizes a mix of platforms, strengthens workforce and shipyard capacity, and reinforces accountability for delivering ships on time. That is a plan for future capability, whose execution depends on the industrial capacity to build and support the ships.

In 2026 testimony to Congress, the Government Accountability Office (GAO) reported that Navy and Coast Guard shipbuilding programs were collectively billions of dollars over cost and years behind schedule. GAO identified proposed responses involving workforce wages, management changes and completing designs before construction, while warning there was no single solution.

GAO also found that maintenance delays and idle time cost the attack-submarine fleet more than 15,000 operational days during fiscal years 2016 through 2025. It estimated $3.4 billion in costs to sustain crews and submarines that provided no operational capability during those delays. Idle time is a period when a submarine and its crew must remain at the pier because they are no longer certified for normal operations and cannot enter a maintenance period. Those delays represent lost use of ships already built, a different problem from deciding how many new ships to order.