The North Atlantic Treaty Organization (NATO)
Formed in 1949 with the signing of the Washington Treaty, NATO is a security alliance of 29 countries from North America and Europe. NATO's fundamental goal is to safeguard the Allies' freedom and security by political and military means. NATO remains the principal security instrument of the transatlantic community and expression of its common democratic values. It is the practical means through which the security of North America and Europe are permanently tied together. NATO enlargement has furthered the U.S. goal of a Europe whole, free, and at peace.
Article 5 of the Washington Treaty -- that an attack against one Ally is an attack against all -- is at the core of the Alliance, a promise of collective defense. Article 4 of the treaty ensures consultations among Allies on security matters of common interest, which have expanded from a narrowly defined Soviet threat to the critical mission in Afghanistan, as well as peacekeeping in Kosovo and new threats to security such as cyber attacks, and global threats such as terrorism and piracy that affect the Alliance and its global network of partners.
In addition to its traditional role in the territorial defense of Allied nations, NATO leads the UN-mandated International Security Assistance Force (ISAF) in Afghanistan and has ongoing missions in the Balkans and the Mediterranean; it also conducts extensive training exercises and offers security support to partners around the globe, including the European Union in particular but also the United Nations and the African Union.