The North American Aerospace Defense Command (NORAD) was established as a result of an agreement between Canada and the United States to defend against increasing Soviet military capabilities. In the early years of World War II, the leaders of the United States and Canada agreed to military cooperation, thus beginning strong defense relations still evident today. Military and civilian personnel from both countries work together for the defense of North America. Established as a formal military command in 1958, NORAD has been headquartered in Colorado Springs since its inception. In the late 1950s, a decision was made to move the Continental Air Defense Command combat operations center to an underground facility to provide a secure and hardened location for air defense operations. After several locations were evaluated, Cheyenne Mountain, south of Colorado Springs, Colorado, was chosen for the new command center. In operation since 1966, Cheyenne Mountain Air Force Station continues to be America's fortress.