What Is NATO’s Article 5?

On September 12, 2001, Article V of the NATO agreement was invoked for the first and only time in response to the September 11, 2001 attacks against the United States of America. An excerpt from the article:

"The article, as the cornerstone of a charter signed in 1949, establishes solidarity among member states and has been invoked only once.

Article 5 is the cornerstone of the North Atlantic Treaty Organization (NATO) and states that an attack on one member of NATO is an attack on all of its members. But despite its importance, NATO has only invoked Article 5 once in its history—in response to the terrorist attacks of September 11, 2001.

NATO and Article 5 were established in 1949 in the aftermath of World War II when communist movements supported by the Soviet Union posed a serious threat to democratically elected governments all over a devastated Europe. In 1948, the Communist Party of Czechoslovakia overthrew that nation’s democratic government, while in Germany, Soviet authorities blockaded the Allied-controlled section of Berlin in an attempt to strengthen their position there."