With bigger and more heavily armed vessels than any other navy in the world, the US Navy is a force to be reckoned with.

To best allocate these resources, the Navy uses an organizational structure comprised of seven active, numbered fleets, or organizations of warships under a single command.

Numbered fleets consist of ships, submarines and aircraft, and are led by vice admirals. A US naval fleet at sea is equivalent to a US Army corps on land.

The Navy's forces were redesignated into numbered fleets during World War II. The fleets were assigned to geographic locations, with even-numbered fleets specific to the Atlantic Ocean and odd-numbered fleets specific to the Pacific Ocean. Each fleet is subdivided into smaller task organizations.

The Navy's active fleets include the Second Fleet, the Third Fleet, the Fourth Fleet, the Fifth Fleet, the Sixth Fleet, the Seventh Fleet and the Tenth Fleet.

The seven active fleets' designations have some numerical gaps because some fleets have been deactivated or merged with others since their establishment in the 1940s.

Numbered fleets

The Second Fleet, based out of Naval Station Norfolk in Norfolk, Virginia, operates assigned ships, aircraft and landing forces on the East Coast and in the northern Atlantic Ocean.

It also coordinates maritime, joint and combined operations and trains maritime forces to respond to global contingencies and help partners in times of need against common adversaries.

Meanwhile, the Third Fleet, which operates out of Naval Base Port Loma in San Diego, California, oversees an area of responsibility that includes the eastern and northern Pacific Ocean areas, including the Bering Sea, Alaska, the Aleutian Islands and a sector of the Arctic.

The Fourth Fleet or USNAVSOUTH, headquartered out of Naval Station Mayport in Florida, is responsible for naval operations in South America, Central America and the Caribbean. Such operations include Navy and joint exercises, counter-illicit-trafficking operations, port visits, humanitarian missions and disaster relief.

The Fifth Fleet, also known as NAVCENT, operates out of Naval Support Activity Bahrain. It is responsible for maritime security in the Central Region, which links the Mediterranean and Pacific through the western Indian Ocean and three strategic chokepoints.

The Sixth Fleet is responsible for naval support of the US European Command and US Africa Command. It is based out of US Naval Activity Support Naples in Italy.

The Sixth Fleet's mission is to “conduct the full range of maritime operations and theater security cooperation in concert with coalition, joint, interagency and other partners in order to advance security and stability in Europe and Africa," according to its website.

The Seventh Fleet, the largest of the Navy’s forward-deployed fleets, is responsible for a US naval operation area spanning more than 124 million square kilometers in the Indo-Pacific, stretching from the International Date Line to the India-Pakistan border and from the Kuril Islands in the north to the Antarctic in the south.

It is headquartered out of US Fleet Activities Yokosuka in Japan.

Rather than a geographic area, the Tenth Fleet, or US Fleet Cyber Command, is responsible for Navy information network operations, offensive and defensive cyberspace operations, space operations and signals intelligence.

Established in 2010, the Tenth Fleet serves as the Navy component for the US Cyber Command and is headquartered out of the Maritime Operations Center in Fort George Meade in Maryland.

Task forces

Each fleet is subdivided into smaller task organizations as fleets themselves are typically too large to carry out specific operations, while individual ships and submarines are usually too small, according to the Department of Defense.

To better implement specific orders, each fleet's ships are divided into task forces, task groups, task units and task elements.

Task forces can be responsible for a wide variety of functions.

For example, the Fifth Fleet consists of eight task forces focused on strike, contingency response, mine warfare, surface, expeditionary combat, unmanned systems and logistics.

Task forces are then further subdivided into progressively smaller task groups, task units and task elements, respectively, each with a narrower operational focus.

This operational structure allows for the Navy to allocate resources when and where they are needed.

"These fleets and their subordinate task organizations have the distinct advantage of flexibility," according to the Navy.

"They can easily be formed to address a specific operational need and similarly dissolved after their objective has been met or another priority arises."