The North Atlantic Treaty Organization (NATO) is an intergovernmental military partnership based on the North Atlantic Treaty which was signed in 1949. The organization comprises of a system of combined defense whereby its member agree to a mutual assault in response to an attack by any foreign party. NATO's headquarter is located in Brussels, Belgium, one of the 28 member states across North America and Europe. An additional 22 countries participate in NATO's "joint venture for Peace", with 15 other states involved in institutionalized discourse programs. The combined military spending of all NATO members constitutes over 70% of the world's defense spending [30].