The Royal Navy of the United Kingdom is the oldest of the British armed services (and is therefore the Senior Service). From the early 18th century to the middle of the 20th century, it was the largest and most powerful navy in the world, playing a key part in establishing the British Empire as the dominant power of the 19th and early 20th centuries. In World War II, the Royal Navy operated almost 600 ships. During the Cold War, it was transformed into a primarily anti-submarine force, hunting for Soviet submarines, mostly active in the North Atlantic Ocean. With the collapse of the Soviet Union, its role for the 21st century has returned to focus on global expeditionary (blue water) operations.
The Royal Navy is the second-largest navy in NATO in terms of the combined tonnage of its fleet. Its global power projection capabilities are deemed second only to the United States Navy. There are currently 91 commissioned ships in the Royal Navy, including aircraft carriers, submarines, mine counter-measures and patrol vessels. There are also the support vessels of the Royal Fleet Auxiliary.
The Royal Navy is a constituent component of Her Majesty's Naval Service, which also comprises the Royal Marines, Royal Fleet Auxiliary and associated reserve forces under command. The Naval Service had 38,710 regular personnel as of November 2006.