How does a country become a member of NATO?
What is the purpose of NATO?
What is the Membership Action Plan (MAP) in NATO?
What are the non-military requirements for NATO membership?
What is required for a country to become a NATO member after talks?
The North Atlantic Treaty Organization, commonly referred to as NATO, was created in 1949 by 12 countries as a military alliance between North America and Europe to protect its members against attack. Since its inception in the wake of World War II, the alliance has grown to 32 countries, with Finland and Sweden being the most recent additions in 2023 and 2024, respectively. The Russian invasion of Ukraine in 2022 spurred Sweden and Finland to seek NATO membership and has spurred discussion about whether Ukraine could become the 33rd member nation. What would Ukraine need to do to become a NATO member? It’s complicated; read on.
The process
Most countries considering applying for NATO membership start with a Membership Action Plan (MAP). A MAP is a guidance program that NATO offers to help prepare countries for meeting the many obligations laid out in its two most important documents, the North Atlantic Treaty (sometimes called the Washington Treaty) and the 1995 Study on NATO Enlargement. These commitments are extensive: The 1995 study mentions “over 1,200 agreements and publications that new members should undertake to comply with” in order to ensure their military can be successfully integrated with others in the alliance.
Moreover, NATO has additional requirements that are not military-related but legal, political, and economic. Simply put, every NATO member-state must be committed to advancing democratic principles and taking steps toward a free-market economy. A country which lacks, for example, sufficiently free elections would have to undergo electoral reforms before NATO would consider its application. While having a MAP can provide a would-be member nation with advice, support, and feedback, it’s important to understand that one is not required and that successfully completing a MAP does not guarantee a country acceptance into the alliance.
An aspiring member-state may decide instead to proceed directly to the first step of the formal admissions process, known as the accession talks. The accession talks are discussions in which NATO representatives ensure that the country’s representatives understand all of the commitments, rights, and obligations involved in NATO membership. During these talks, NATO officials notify the country’s representatives of any changes that will need to be made in order to meet the alliance’s standards. After the talks, the country’s government sends a formal letter of intent to NATO’s secretary-general. This letter lays out a timetable for completing whatever changes the country will have to implement.
That done, the next step is for all of NATO’s member-states to sign and ratify the accession protocols. Accession protocols are essentially amendments or additions to the North Atlantic Treaty that bind the alliance together; they change the treaty so that the applying country is allowed to join it. Each NATO member-state ratifies the protocols just as it would any treaty with foreign governments, by sending the protocols to its national legislature for passage. In the United States, for example, two-thirds of the Senate would have to vote in favor of the protocols to pass them.
Hurdles to ratification
The ratification of the accession protocols is perhaps the most fraught step in the admissions process. Since a new country’s membership in NATO would obligate all of the alliance’s member-states to defend that country in case of an attack, the member-states must unanimously approve the new country’s inclusion. Because ratifying the accession protocols is a purely political decision, any member-state may refuse to sign for any reason.
A NATO member-state might therefore choose to block a new country’s admittance into the alliance because of some unrelated grievance. Sweden’s acceptance, for instance, was stalled by Turkey and Hungary because Sweden granted political asylum to Kurdish dissidents. If every NATO member-state signs and ratifies the protocols, then the applicant nation needs only to have its own legislature ratify the treaty. Once the instrument of accession (a legal document) is delivered to the U.S. Department of State, which serves as NATO’s depository, the country becomes an official NATO member.
How long this entire process takes can vary quite a bit. For example, North Macedonia began the process in 1999 but did not gain NATO membership, because of disagreements with Greece, until 2020, but Finland’s NATO membership was approved in less than a year. The possibility of Ukraine joining NATO dates to the early 1990s, and NATO as an organization has long said that Ukraine’s future includes NATO membership. In the wake of the 2022 Russian invasion, Ukrainian Pres. Volodymyr Zelensky has asked that the process be fast-tracked. Since the start of the war, NATO has supported Ukraine and decried Russian aggression. However, in 2025 U.S. Defense Secretary Pete Hegseth stunned NATO allies by announcing that “the United States does not believe that NATO membership for Ukraine is a realistic” end of the war. For his part, Zelensky has said that he would resign from the presidency in order to gain NATO membership for Ukraine.
