At Turkey`s request, NATO has implemented collective defence measures three times: in 1991 with the deployment of Patriot missiles during the Gulf War, in 2003 with the agreement on a set of defence measures and the implementation of Operation Display-Dissuasion during the Iraq crisis and in 2012 in response to the situation in Syria with the deployment of Patriot missiles. When Article 5 was drafted in the late 1940s, there was consensus on the principle of mutual assistance, but there were substantive differences of opinion on how to implement this obligation. European participants wanted to ensure that the United States automatically came to the aid if one of the signatories was attacked; the United States did not want to make such a commitment and obtained that this was reflected in the text of Article 5. Contracting parties may unanimously invite any other European state capable of supporting the principles of this treaty and contributing to the security of the North Atlantic to accede to this treaty. Any state so invited can become a party to the treaty by filing its instrument of membership with the government of the United States of America. The Government of the United States of America informs each of the contracting parties of the filing of any accession instrument. On 16 April 2003, NATO agreed to take command of the International Security Assistance Force (ISAF) in Afghanistan, which includes troops from 42 countries. The decision was taken at the request of Germany and the Netherlands, the two states that were leading ISAF at the time of the agreement, and the 19 NATO ambassadors unanimously approved it. The transfer of control to NATO took place on 11 August and marked the first time in NATO`s history that it led a mission outside the North Atlantic.  This treaty is ratified and its provisions are implemented by the contracting parties in accordance with their respective constitutional procedures. The ratification instruments are filed as soon as possible with the Government of the United States of America, which informs all other signatories of any filing.
The treaty will enter into force between the states that have ratified it as soon as the ratifications of most of the signatories, including those of Belgium, Canada, Luxembourg, the Netherlands, the United Kingdom and the United States, have been tabled and will enter into force for other states on the date of the tabling of their ratifications.