Ulchi-Freedom Guardian is the name of the military exercise previously known as Ulchi-Focus Lens, a combined military exercise between South Korea and the United States. The exercise is the world's largest computerized command and control implementation, involving 50,000 South Korean troops alongside 17,500 U.S. troops in 2017, and mainly focuses on defending South Korea from a North Korean attack. The exercise was initiated in 1976 and is conducted annually during August or September. The word 'Ulchi' comes from the name of a famous Korean general called Ŭlchi Mundŏk, who was the Commander-In-Chief of the army of Goguryeo.