The military of the United States was a naval-based advanced military with by far the highest military expenditure in the world. The United States Navy was the world's largest navy, with the largest number of aircraft carriers, bases all over the world (particularly in an incomplete "ring" bordering the Warsaw Pact states to the west, south and east). The US had the largest nuclear arsenal in the world during the first half of the Cold War, one of the largest armies in the world and one of the two largest air forces in the world. Its powerful military allies in Western Europe (the North Atlantic Treaty Organisation states) had their own nuclear capabilities. The US also possessed a powerful global intelligence network in the Central Intelligence Agency.