What is NATO Which countries are members of NATO Who can become a member of NATO How did NATO expand historical background by year
What is NATO
NATO is an international military political organization. In English the acronym represents the North Atlantic Treaty Organization, commonly translated as the same name in full.
1949
An alliance was formed to counterbalance the influence of the Soviet Union.
The alliance aims to guarantee the security and freedom of its member states. It uses both military and political tools to achieve this goal.
The central document is the North Atlantic Treaty, which states the principle of collective defense in Article 5. It says that an attack on one or more NATO members is an attack on the entire alliance, and other allies commit to assisting the threatened country.
Throughout NATO’s history, Article 5 has been invoked once. The United States called for support from its allies after the September 11, 2001, attacks on the World Trade Center in New York by the terrorist network al Qaeda.
Which countries are members of NATO?
At its founding in 1949 NATO included twelve countries: Belgium, Canada, Denmark, France, Iceland, Italy, Luxembourg, the Netherlands, Norway, Portugal, the United Kingdom and the United States. Over time new members joined, and today NATO comprises thirty two states.
NATO members as of 2024 include:
- Albania;
- Belgium;
- Bulgaria;
- Hungary;
- Germany;
- Greece;
- Denmark;
- Iceland;
- Spain;
- Italy;
- Canada;
- Latvia;
- Lithuania;
- Luxembourg;
- Netherlands;
- Norway;
- Poland;
- Portugal;
- Romania;
- North Macedonia;
- Slovakia;
- Slovenia;
- United Kingdom;
- United States;
- Türkiye;
- Finland;
- France;
- Croatia;
- Montenegro;
- Czech Republic;
- Sweden;
- Estonia.
Georgia, Ukraine and Bosnia and Herzegovina are candidates for membership. The prospect of accession often sparks debate about potential political consequences within the alliance.
The total manpower across member countries is about 3.36 million, and the collective military budget is roughly 1.26 trillion dollars.
Who can become a member of NATO?
The alliance follows an open door policy outlined in Article 10 of the Washington Treaty. Any European country that contributes to the security of the North Atlantic area can join NATO.
Invitations are extended by the North Atlantic Council with the consensus of all current members.
Prospective members are expected to meet political, economic and military benchmarks to ensure they can contribute to and benefit from alliance security, and they must share the principles enshrined in the North Atlantic Treaty.
Since 1999 the first step toward membership is the Membership Action Programme MAP, which outlines the changes needed to prepare a state for alliance membership.
How NATO expanded: historical background by year
From its birth in 1949 NATO has grown significantly. It began as a defensive bloc against possible Soviet aggression and then expanded as countries sought stronger defense guarantees in the face of changing geopolitical realities. After the USSR collapsed, Western nations assured Moscow they would not push the alliance toward Russia’s borders.
Expansion occurred in stages, each driven by geopolitical shifts and the desire of nations to bolster their defense capabilities.
1949: Founding of NATO
On April 4, 1949, twelve nations signed the North Atlantic Treaty, marking the start of NATO. The founders included the United States, Canada and ten Western European states: Belgium, United Kingdom, Denmark, Iceland, Italy, Luxembourg, the Netherlands, Norway, Portugal, and France. The main aim was collective defense against possible Soviet aggression.
1952: Greece and Türkiye
NATO’s first expansion occurred in 1952 with the entry of Greece and Turkey. Their admission strengthened NATO’s southern flank amid rising tensions in the Eastern Mediterranean and concerns about Soviet ambitions in the region.
1955: West Germany
West Germany joined NATO in 1955, a pivotal step in postwar reconstruction and Western integration. The move drew a stern response from the Soviet Union and helped trigger the formation of the Warsaw Pact, a counterpart bloc under Moscow’s influence.
1982: Spain
Spain joined NATO in 1982 as part of its democratic transition after Franco, with the integration approved following a 1986 referendum reflecting the country’s move into Western institutions.
1999: First post Soviet enlargement — Poland, Czech Republic and Hungary
After the Cold War, NATO began eastward expansion as former Warsaw Pact members joined. The first wave included Poland, the Czech Republic and Hungary on March 12, 1999, signaling a new era of alliance expansion.
2004: Largest eastern enlargement
In 2004 seven countries—Bulgaria, Estonia, Latvia, Lithuania, Romania, Slovakia and Slovenia—joined NATO. This expansion covered a broad part of Eastern Europe, including several former Soviet republics, marking the alliance’s biggest eastward growth to date.
2009: Albania and Croatia
Albania and Croatia became NATO members on April 1, 2009, a milestone for stabilizing the Balkans and integrating the region into Euro-Atlantic structures after the 1990s conflicts.
2017: Montenegro
Montenegro joined NATO on June 5, 2017, following years of reform and efforts to strengthen democratic institutions.
2020: North Macedonia
North Macedonia joined NATO on March 27, 2020, after overcoming the long dispute with Greece over the country’s name, a hurdle resolved through diplomatic agreement.
Name dispute in Macedonia
The name issue with Greece affected accession talks from 1991 to 2019, as Greece argued the term Macedonia referred to a historic region and could imply irredentist claims. The resolution in 2019 unlocked further integration steps for North Macedonia.
2022 2024: Finland and Sweden
Amid the Russia-Ukraine conflict, Finland and Sweden sought NATO membership. Finland joined in 2023 and Sweden followed in 2024, marking a new era of Nordic security cooperation.