It has been clear for several years now that what NATO purports to stand for and what certain member states practice, do not fully align. From the beginning in 1949, when treaty values and strategic imperatives have been conflicted, the strategic imperatives have almost always, albeit temporarily on an "exceptional" basis, taken precedence over the values. While not new, these tensions today are greater than at any time in NATO's history. In our view, they could become an existential threat. We use a case study from NATO's history to examine the case of Turkey today. KEYWORDS NATO; value foundations; strategic imperatives I The best-known passage from the North Atlantic Treaty is probably the opening of Article 5: '[t]he Parties agree that an armed attack against one or more of them in Europe or North America shall be considered an attack against them all [.. .],' and NATO's core identity as a security organisation seems widely accepted. 1 However, the treaty articulates both values and a strategic agenda for the alliance. Less well known, but arguably just as important for understanding NATO's nature, are these words from the treaty's preamble: '[t]he Parties to this Treaty. .. are determined to safeguard the freedom, common heritage and civilisation of their peoples, founded on the principles of democracy, individual liberty and the rule of law.' 2 Indeed, one could argue that treaties CONTACT Ruud van Dijk Ruud.