Collective Defence
NATO is a political and military alliance of 32 countries, most recently joined by Finland in 2023 and Sweden in 2024. Its primary purpose is to guarantee the security of its Allies through collective defence. NATO’s decision-making process is based on consensus among all Allies and is coordinated at its headquarters in Brussels, where all member states are represented.
The North Atlantic Council is NATO’s highest political decision-making body, while the Military Committee is its highest military authority. NATO’s military command structure reports to NATO Headquarters, providing military advice and implementing its decisions.
How does NATO operate?
NATO relies on the capabilities provided by its Allies. In the event of a military conflict, the required forces can be assembled based on national contributions and the specific situation.
This forms a collective pool of capabilities that Allies can place under NATO command when required. NATO’s operations and missions are conducted on the basis of these contributions.
NATO’s strategic commanders define the requirements for a given operation, and the Allies meet these requirements by providing the necessary military capabilities, which are then placed under NATO command.
NATO’s military command structure reports to NATO Headquarters, where it provides military advice and carries out decisions.
NATO's Strategic Foundation Documents
The North Atlantic Treaty, also known as the Washington Treaty (1949), is the founding document of the Alliance. It establishes, at a general level, the rights and obligations of NATO member states, including Article 5 on collective defence.
The original text of the Treaty on NATO’s website
The Treaty on the Riigi Teataja website (in estonian)
NATO’s Strategic Concept is a comprehensive document that sets out the Alliance’s strategic direction. The current Strategic Concept was approved by Allied leaders in 2022. It reaffirms that NATO’s primary purpose is to ensure the collective defence of its Allies, based on a 360-degree approach. The Concept defines the Alliance’s three core tasks: deterrence and defence; crisis prevention and management; and cooperative security.
Key Decisions from NATO Summits
The annexation of Crimea by the Russian Federation in 2014, followed by the conflict in eastern Ukraine, marked a significant shift for NATO. The Alliance’s focus returned from international operations and crisis management to its core mission: deterrence and defence on European territory.
At the 2016 Warsaw Summit, NATO Allies decided to deploy permanent battlegroups on the Alliance’s eastern flank – in Estonia, Latvia, Lithuania, and Poland. The Allied battlegroup in Estonia has been in place since 2017, with the United Kingdom serving as the framework nation.
The Russian Federation’s full-scale war against Ukraine, which began on 24 February 2022, has fundamentally changed the security situation in the Euro-Atlantic area. At the subsequent NATO Madrid Summit in June 2022, a new NATO Strategic Concept was adopted, identifying the Russian Federation as the most significant and direct threat to the security, peace, and stability of the Euro-Atlantic region. The Madrid Summit also decided to strengthen NATO’s defensive posture and to deploy additional brigade-size units to protect the eastern flank. Since 2022, the United Kingdom has served as the framework nation for the reinforcement brigade assigned to Estonia.
At the 2023 Vilnius Summit, NATO confirmed new regional defence plans. The Summit also hosted the first meeting of the NATO–Ukraine Council, aimed at demonstrating NATO’s unity in providing political and practical support to Ukraine.
The 2025 NATO Hague Summit focused primarily on increasing member states’ defence spending and enhancing military capabilities. The most significant decision was an agreement among Allied leaders to raise defence spending to 5% of national GDP by 2035 at the latest. Under this agreement, Allies are expected to allocate at least 3.5% of GDP to military defence, including meeting NATO force targets, and 1.5% of GDP to broader defence and security-related activities.
Support for Ukraine
Since the start of the Russian Federation’s full-scale war against Ukraine on 24 February 2022, NATO Allies have provided Ukraine with extensive political and practical support.
At the 2023 NATO Vilnius Summit, the NATO–Ukraine Council met for the first time, confirming that Ukraine’s path to NATO membership is irreversible.
At the 2024 Washington Summit, Allies agreed to establish the NATO Security Assistance and Training Mission for Ukraine (NSATU), which coordinates the military aid, training, and logistics provided by Allies to Ukraine.
In 2025, an additional initiative, the Prioritized Ukraine Requirements List (PURL), was launched to support Ukraine. Through this initiative, NATO coordinates the procurement of critical defence equipment and supplies from the United States. The initiative is funded by NATO Allies and partners, and the delivery of assistance to Ukraine is coordinated, among other channels, through NSATU.
Cooperation among Allies
Following the approval of NATO’s new Force Model at the NATO Defence Ministers’ meeting in February 2022, the previous concepts of the NATO Response Force (NRF) and the NATO Readiness Initiative (NRI) were phased out as of 1 July 2024. They have been replaced by a revised concept: the lighter and more mobile Allied Reaction Force (ARF), which is maintained at readiness to conduct military operations both within and beyond the area of responsibility of NATO’s Supreme Allied Commander Europe (SACEUR).
The ARF carries out operations across all domains and is composed of forces contributed by NATO Allies. In addition to deterrence and defence activities on land, the ARF focuses on air, maritime, and cyber domains. Permanent NATO naval units (Standing Naval Forces, SNF), which were part of the NRF under the previous force structure until July 2024, remain at high readiness under the new Force Model. They are not permanently assigned to the ARF, but Allied contributions to the SNF can be employed in ARF operations with the consent of the contributing Allies.
Estonia has participated in NATO response forces since 2005. In 2010, Estonia contributed a company-sized land component within the Baltic Battalion, and the same contribution was made in 2016.
At the Warsaw Summit in June 2016, NATO leaders decided, in response to the changed security environment, to deploy permanent battlegroups to NATO’s eastern flank in Estonia, Latvia, Lithuania, and Poland.
The Allied battlegroup that arrived in Estonia in spring 2017 and is based in Tapa comprises over 1,000 Allied personnel. The United Kingdom serves as the framework nation for the battlegroup, with France also contributing forces.
At the Madrid Summit in 2022, it was decided to assign additional brigade-sized units for the defence of NATO’s eastern flank countries. In 2022, the United Kingdom pledged to act as the framework nation for a reinforcement brigade designated for Estonia, providing a unit permanently based in the UK that would be deployed to Estonia in the event of a crisis or conflict, as well as during regular exercises.
The NATO Air Policing mission is a peacetime operation aimed at ensuring the security of Allied airspace and providing a rapid response to any potential violations of NATO airspace.
Since 2004, the NATO Air Policing mission has been conducted from the Baltic States. Aircraft safeguarding Baltic airspace are based at Šiauliai Air Base in Lithuania and, since 2014, also at Ämari Air Base in Estonia, from where enhanced air policing is carried out.
Similar to the joint protection of Baltic airspace, Allies also conduct air policing in other NATO eastern flank countries, the Western Balkans, Iceland, and the Benelux countries.
In 2015, Allies decided to establish NATO Force Integration Units (NFIUs) on the territory of NATO eastern flank countries, tasked with supporting the reception, support, and exercises of NATO forces.
The NATO Force Integration Unit based in Tallinn includes not only Estonian Defence Forces personnel but also representatives from Allied countries, including the United States, Germany, and the Netherlands.
Increased reliance on technology means that cyber defence is an integral part of security in the 21st century.
NATO’s Strategic Concept emphasises the importance of cyber defence in protecting NATO’s information and communication systems, and NATO has recognised cyberspace as a domain of operations. Cooperation takes place within the Alliance, with partner countries, and with industry and the academic sector.
In 2008, the NATO Cooperative Cyber Defence Centre of Excellence (CCDCOE) was established in Tallinn, with specialists from more than 35 Allied and partner nations represented.
Last updated: 14.04.2026
