"This thesis analyzes various interpretations of Article 5 of the North Atlantic Treaty since 1949. These variations reflect the evolving conceptions of the national security interests of the NATO Allies. Three historical periods are studied: the Cold War, 1949 to 1989; the post-Cold War, 1989 to 10 September 2001; and since 11 September 2001. The collective defense commitment in Article 5 was the foundation principle of the Alliance. During the Cold War, however, interpretations of collective defense necessarily required adaptation to remain relevant. The adaptability constructed during the Cold War yielded to broader concepts of threats and risks in the post-Cold War period. Following the first invocation of Article 5 due to the 11 September 2001 terrorist attacks on the United States, the actions taken by NATO and the individual Allies demonstrate the value of NATO's collective defense principles. The adaptability of Article 5 throughout NATO's history thus far suggests that in the future it will remain a highly valued and integral component of the Alliance's approach to security."
Naval Postgraduate School, Dudley Knox Library: http://www.nps.edu/Library/index.aspx