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 WWII, 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 a constituent component of the 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.