North Macedonia is set to officially become the 30th member of NATO this week with the deposit of its “instrument of accession” at the U.S. Department of State.

On March 17, the Spanish Senate ratified North Macedonia’s accession protocol, becoming the 29th and final NATO member state to do so. The U.S. Senate by a vote of 91-2 had ratified North Macedonia’s accession protocol on Oct. 22, 2019.

The Heritage Foundation has for many years noted the importance of Macedonia’s accession to NATO.

North Macedonia’s accession is very welcome; its addition strengthens the alliance, bolsters regional stability in the western Balkans, and sends a strong message to pernicious actors—such as Russia—that they do not have a veto right over the decisions of the sovereign member states of NATO.

The U.S. has long led the way on Macedonia’s inclusion in NATO and for the alliance’s open-door policy. That open-door policy for qualified countries has contributed greatly to transatlantic security since the first round of enlargement in 1952 and helped to ensure the alliance’s central place as the prime guarantor of security in Europe.

NATO has also been a crucial driver of modernization and reform in candidate countries, has promoted stability and peace in Europe, and has made it easier for the alliance to coalesce around collective defense.

NATO has done more than any other organization, including the European Union, to promote democracy, stability, and security in the Euro-Atlantic region. That was accomplished by enticing countries to become a part of the club.

Macedonia’s accession to NATO is a milestone for the alliance, the end of a decades-long dispute with Greece over its northern neighbor’s official name, and the successful culmination of U.S. leadership supporting the nation’s NATO aspirations.

In June 2018, the two nations signed the Prespa Agreement, in which the Republic of Macedonia agreed to change its official name to the Republic of North Macedonia. In exchange, Greece dropped its opposition to the country’s accession to NATO and agreed to ratify “any of the Second Party’s accession agreement to International Organizations, of which the First Party is a member.”

On Jan. 11, Macedonia’s parliament passed an amendment to the constitution to change the formal name of the nation to Republic of North Macedonia. Two weeks later, on Jan. 25, the Greek parliament ratified the Prespa Agreement.

While the agreement remains controversial to many in Macedonia, it paved the way for the nation’s long overdue accession to NATO, which is an important milestone for the region and the alliance.

North Macedonia is now the fourth nation from the western Balkans to join NATO (Albania, Croatia, and Montenegro are the others), a region which retains significant ethnic, religious, and cultural differences, along with historical grievances, and which has benefited greatly from the stability NATO has engendered.

North Macedonia’s joining of NATO leaves only two official candidate countries left: Bosnia and Herzegovina, and Georgia. U.S. leadership will remain the critical element for ensuring that NATO’s open door remains accessible to deserving European nations.