That's because it was written before Turkey and Greece were part of the treaty. See Note 1 in your link at the bottom, which refers to the "Protocol to the Nort

That's because it was written before Turkey and Greece were part of the treaty. See Note 1 in your link at the bottom, which refers to the "Protocol to the North Atlantic Treaty on the Accession of Greece and Turkey": http://www.nato.int/cps/de/natohq/official_texts_17245.htm http://www.nato.int/cps/de/natohq/official_texts_17245.htm - which modifies Article 6 of the original treaty. (to "For the purpose of Article 5, an armed attack on one or more of the Parties is deemed to include an armed attack: on the territory of any of the Parties in Europe or North America, on the Algerian Departments of France, on the territory of Turkey or on the islands under the jurisdiction of any of the Parties in the North Atlantic area north of the Tropic of Cancer; [...]")