Washington Treaty

The Washington Treaty, also referred to as the North Atlantic Treaty, is the foundation document of NATO. This treaty, which consists of 14 articles, was signed on 4 April 1949 in Washington, DC, the capital of the United States, by 12 European and North American countries: Belgium, Canada, Denmark, France, Iceland, Italy, Luxembourg, Netherlands, Norway, Portugal, United Kingdom and the United States. See also photos of the treaty being signed.
The treaty laid the foundation for collective defence between member countries, which treats an armed attack against one or more member as an attack against all members. The principle of collective defence in the Washington Treaty is based on Article 51 of the UN Charter, which states that in the event of an armed attack, countries have the right to individual and collective self-defence until the UN Security Council has taken the necessary measures to ensure international peace and security.
Article 5 of the Washington Treaty sets out the primary objective of NATO’s activities – to secure and protect the security and freedom of its member countries by political and, if necessary, military means. The Washington Treaty also sets out a number of other principles and rules essential for cooperation to ensure national security, as well as procedures for consultation. The Treaty is also the foundation document of NATO’s governing body, the North Atlantic Council, and establishes the procedure for new member countries that want to join NATO. A country can only join the Washington Treaty if all the countries that are already members agree to it.
The Estonian version of the Washington Treaty can be read here