North Atlantic Treaty Organization (NATO) has been characterized by an inconstant, or even incongruous, evolution; but in the early 21st century rifts among member states have turned stronger and, as a result, more worrisome. Since its inception NATO has alternated phases of enthusiasm, with the allies demonstrating a palpable sense of unity and solidarity, and periods of standstill, ill-concealed uneasiness, or, worse, open criticism toward the choices of one or more of their partners. NATO played a key role in the 2011 Libyan conflict and continues to act as Europe’s major defense and security organization, especially since Russia’s involvement in eastern Ukraine and its illegal annexation of Crimea in 2014. The life of NATO is punctuated by a series of tensions that, in the most recent times, seem to have reached a degree of unprecedented intensity. NATO’s history appears punctuated by a constellation of episodes showing the cyclical nature of inter-allied crises.