Twelve nations sign the North Atlantic Treaty creating the North Atlantic Treaty Organization.

The North Atlantic Treaty Organization (NATO) was established on April 4, 1949, with the signing of the North Atlantic Treaty (also known as the Washington Treaty) by 12 founding countries: the United States, Canada, the United Kingdom, France, Italy, Belgium, the Netherlands, Luxembourg, Norway, Denmark, Portugal, and Iceland. Created in the aftermath of World War II, NATO aimed to provide collective security against the growing threat of Soviet expansion during the early Cold War. The principle of collective defense, enshrined in Article 5 of the treaty, asserts that an armed attack against one member is considered an attack against all, compelling mutual defense. NATO expanded throughout the Cold War, particularly after the fall of the Berlin Wall and the dissolution of the Soviet Union, incorporating former Eastern Bloc countries into the alliance. This expansion, along with NATO’s evolving role in global security, peacekeeping missions, and counter-terrorism efforts, has shaped its significance as a prominent international military alliance in the 21st century.