Player Embed Code: Download Embed Share How Does a Country Join NATO? Defense.gov Oct. 2, 2018 | 2:22 From the essential pre-requisites to the final national bill of ratification, accession into NATO can be summed up in five simple steps. Built into the very text of NATO’s founding treaty, it has always been possible for new members to join the Alliance with the unanimous agreement of all existing Allies. The Membership Action Plan (MAP) was created to streamline the process and help countries aspiring to join NATO in their preparations for potential membership.Now, with the most recent addition of Montenegro, NATO has grown from an original group of 12 to 29 member states. This animation sums up the series of steps it takes for a candidate country to become a full member of NATO, recognized both nationally and internationally.