Walker Air Force Base is a closed United States Air Force base located three miles (5 km) south of the central business district (CBD) of Roswell, a city in Chaves County, New Mexico, US. Opened in 1941 as an Army Air Corps flying school, it was active during World War II and the postwar era as Roswell Army Air Field. During the early years of the Cold War, it became the largest base of the Strategic Air Command. It is also known for the Roswell UFO incident, an event that supposedly happened on 4 July 1947. It is alleged that a "flying disk" crashed during a severe thunderstorm near the base at Corona, New Mexico.