armed attack against any of them by Russia would trigger Article 5 of NATO’s founding charter, which states: ‘An armed attack against one or more [NATO member states] in Europe or North America shall be considered an attack against them all’, and goes on to say NATO will come to the rescue if necessary. Article 5 was invoked after the terrorist attacks in the USA on 11 September 2001, paving the way for NATO involvement in Afghanistan.
