The North American Air Defense Agreement (NORAD) was a pact made in 1957, at the height of the Cold War. It placed under joint command the air forces of Canada and the United States. Its name was later changed to the North American Aerospace Defense Command; but it kept the NORAD acronym. Canada and the US renewed NORAD in 2006, making the arrangement permanent. It is subject to review every four years, or at the request of either country. NORAD’s mission was also expanded into maritime warnings. The naval forces of the two countries remain under separate commands.