The United States Navy traces its origins to the Continental Navy, which was established during the American Revolutionary War and was disbanded shortly thereafter. The United States Constitution, though, provided the legal basis for a seaborne military force by giving Congress the power "to provide and maintain a navy." Depredations against American shipping by Barbary Coast corsairs spurred Congress to employ this power by passing the Naval Act of 1794 ordering the construction and manning of six frigates. The U.S. Navy came into international prominence in the 20th century, especially during World War II. It was a part of the conflict from the onset of American military involvement — the Attack on Pearl Harbor — to Japan's official surrender on the deck of the USS Missouri. The U.S. Navy had a role in the subsequent Cold War, in which it evolved into a nuclear deterrent and crisis response force while preparing for a possible global war with the Soviet Union.

The 21st century United States Navy maintains a sizable presence in the world, deploying in such areas as East Asia, Southern Europe, and the Middle East. Its ability to project force onto the littoral regions of the world, engage in forward areas during peacetime, and rapidly respond to regional crises makes it an active player in American foreign and defence policy. The U.S. Navy continues to spend more on technology development than any other and is the world’s largest navy with a tonnage greater than that of the next 17 largest combined.
The Navy is administratively managed by the Department of the Navy, which is headed by the civilian Secretary of the Navy. The Department of the Navy is, itself, a division of the Department of Defense, which is headed by the Secretary of Defense. The highest ranking Navy officer is the Chief of Naval Operations.

Organization :

The Navy falls under the administration of the Department of the Navy, under civilian leadership of the Secretary of the Navy. The most senior naval officer is the Chief of Naval Operations (CNO), a four-star admiral who is immediately under and reports to the Secretary of the Navy. At the same time, the Chief of Naval Operations is one of the Joint Chiefs of Staff, which is the second-highest deliberatory body of the armed forces after the United States National Security Council, although it only plays an advisory role to the President and does not nominally form part of the chain of command. The Secretary of the Navy and Chief of Naval Operations are responsible for organizing, recruiting, training, and equipping the Navy so that it is ready for operation under the command of the Unified Combatant Commanders.

Operating forces :

There are nine components to the operating forces of the U.S. Navy: Atlantic Fleet, Pacific Fleet, Naval Forces Central Command, Naval Forces Europe, Naval Network Warfare Command, Navy Reserve, Naval Special Warfare Command, Operational Test and Evaluation Forces, and Military Sealift Command.[13] Fleets in the United States Navy take on the role of force provider; they do not carry out military operations independently, rather they train and maintain naval units that will subsequently be provided to the naval forces component of each Unified Combatant Command. While not widely publicized, groups of ships departing U.S. waters for operational missions gain a Task force type designation, almost always with the Second or Third Fleets. On entry into another numbered fleet's area of responsibility, they are redesignated as a task group from that fleet. For example, a carrier task group departing the Eastern Seaboard for the Mediterranean might start out as Task Group 20.1; on entry into the Mediterranean, it might become Task Group 60.1.