According to Article 3 of the NATO Treaty (North Atlantic Treaty 1949), the member states must maintain both their own and their collective ability to defend themselves against armed attacks. However, Finland decides on the implementation principles of its own defence and is primarily responsible for defending its own territory, but it will receive help from other NATO countries if necessary.

NATO’s deterrence and defence are of fundamental importance to Finland’s security. The significance of NATO membership and the security guarantee this membership brings raises the threshold of attacking Finland. On the other hand, Finland’s strong defence capability and crisis resilience also strengthen the alliance. According to the Government’s Defence Report, Finland will maintain and develop a strong national defence capability based on general conscription and comprehensive national defence in all circumstances. Finland’s military defence is coordinated with and complements NATO’s deterrence and defence.

According to the Government’s Report on Foreign and Security Policy, Finland is committed to NATO’s deterrence and common defence across the entire alliance and with all threat scenarios in mind. As a member of NATO, Finland is prepared to support other NATO countries. Finland also actively participates in the development of NATO’s nuclear weapons policy. When applying for NATO membership, Finland did not set any restrictions on participation in the alliance’s activities. NATO has announced that it will be a nuclear alliance as long as nuclear weapons are in use elsewhere.

NATO’s common defence is a new statutory task for the Finnish Defence Forces. This means that the Defence Forces will participate in NATO’s defence planning and operational planning processes, as well as in the command-and-control arrangements, exercises and operational activities required by it.

As a NATO member, Finland participates in the planning of NATO’s common defence. The NATO Defence Planning Process (NDPP) operates on a four-year cycle, and its purpose is to develop the joint capabilities of the member states and NATO as a whole. During 2025, new capability targets for defence planning will be established for all member states. They are binding on the member states, which means that they will be included in the Finnish Defence Forces’ development programme. Finland participates in NATO’s peacetime collective defence tasks, other NATO military activities, and sends personnel to serve in NATO structures and headquarters. The number of personnel needed for this is estimated to be around 100–200.

Finland’s defence is part of NATO’s common defence, so the key functions of Finland’s defence are linked to NATO’s common structures and operating models. If necessary, Finland must be able to send troops to help another NATO country and receive troops from NATO member states. For Finland, it is essential to enable the arrival and effective operation of allied forces on Finnish territory. The Defence Forces must also develop the deployability of their own troops outside Finland in a manner that meets NATO requirements. According to the Defence Report, it will be investigated whether changes to the composition, or command and control of the Defence Forces are needed due to NATO membership obligations, including the defence responsibilities toward other NATO countries.

Finland is part of NATO’s command-and-control structure, and Finnish territory falls within the area of responsibility of NATO’s Supreme Allied Commander Europe (SACEUR). Finland maintains national operational plans for the defence of its own territory, and these plans serve as the foundation for NATO’s regional planning and operations. Finland is also integrated into NATO’s joint air and missile defence system.

The exchange of intelligence with other NATO countries is increasing. Finland participates in maintaining NATO’s common situational awareness and intelligence gathering and receives information on the military operating environment through NATO. One example of operational-level intelligence cooperation is the conduct of surveillance and reconnaissance flight operations in Finnish airspace together with key allies.

NATO’s peacetime missions are carried out with the Forward Land Forces (FLF) on the eastern flank of the alliance, the Standing Naval Forces (SNF), and the Air Policing and Air Shielding missions of air defence.

NATO is establishing command echelons of land, sea and air operations in Northern Europe supported by regional expertise. These command echelons are subordinated to Joint Force Command in Norfolk, USA. On 5 December 2025, Finland, Sweden and Denmark were transferred to the area of responsibility of the operational command JFC Norfolk. Before that, JFC Brunssum was responsible for them. Norway and Iceland were already under Norfolk’s leadership.

A Multi-Corps Land Component Command (MCLCC) has been established in Finland, and it is responsible for NATO’s ground operations in Northern Europe. The MCLCC is an army-level command that can lead operations involving several army corps. It is located within the Finnish Army Command in Mikkeli and is commanded by the Commander of the Finnish Army, who performs the role in addition to his primary duties. The MCLCC is responsible for NATO’s exercises and other peacetime activities in its area, and in a crisis, it leads NATO’s ground operations in the region. The personnel will consist of both NATO allies and members of the Finnish Defence Forces.

The composition of NATO’s forward FLF ground forces will consider geographical factors and the threat environment. The FLF troops in Finland will be led by Sweden. The backbone of the unit is the Norrbotten Regiment (I 19) based in Boden. The regiment will train and form a mechanised brigade optimised for the Arctic region, consisting of five battalions and support units. The Norrbotten Regiment serves as the centre of subarctic warfare for the Swedish Armed Forces. The other participating countries will be NATO countries that have capabilities suitable for Finland’s conditions and military and political grounds for a long-term commitment to Finland. In addition to Sweden, at least the United Kingdom, France, Norway, Denmark, Iceland, and Italy have announced their participation in this FLF group. Its command structure will be permanently stationed in Finland, but the actual troops will only regularly visit Finland for exercises with Finnish troops. In peacetime, NATO’s ability to rapidly reinforce Finland’s FLF force will also be practiced. The operations of the FLF force are based on NATO’s operational planning, and when readiness is increased, the unit can be strengthened into a brigade. FLF unit operates mainly in Rovaniemi and Sodankylä. The Government’s Defence Report states that the presence of NATO ground forces in Finland will strengthen deterrence and create a uniform forward defence capability on NATO’s border with Russia.

NATO’s naval component in the Baltic Sea is led by the HQ Commander Task Force Baltic (CTF Baltic), established in 2024, which currently operates in conjunction with the German Naval Command in Rostock. In addition to soldiers from Germany, the staff of the Headquarters includes soldiers from Italy, France, the United Kingdom, the Netherlands, Denmark, Sweden, Poland, Lithuania, Latvia, Estonia, and Finland.

Finnish Defence Forces’ troops also participate in NATO’s peacetime multinational naval and air force operations. In 2025, the Finnish Defence Forces participated with one vessel in NATO’s Mine Countermeasures Detachment operation in the Baltic Sea, the North Sea and the North Atlantic, and with a Hamina-class vessel in the operations of NATO’s Standing Naval Detachment in the Baltic Sea, the North Sea and the North Atlantic. In addition, the Finnish Defence Forces participated in NATO’s Air Shielding mission with a detachment of several fighter aircraft operating in Iceland, the Northeast Atlantic and the Arctic Ocean.

Finland has decided to participate in NATO’s multinational MRTT (Multi Role Tanker Transport) programme, which was established by several NATO countries to maintain a multinational air-to-air refuelling and transport aircraft squadron.

NATO has a new rapid reaction force, the Allied Reaction Force (ARF), which is intended to be used for all tasks of the alliance in accordance with the decisions of the NATO Council. Finland is preparing to participate in the activities of the ARF force in the future.

The direct costs of Finnish NATO membership consist of contributions to NATO’s common budgets and participation in NATO activities. The contributions are based on the size of the member states’ economies. Finland’s share of NATO’s budget expenditure is about 0.9 %, which means EUR 70–100 million per year. Joining NATO’s defence planning process and the implementation of the capability goals targeted at Finland, as well as participating in NATO’s operational planning and operations, will bring significant additional costs.

At the NATO summit in 2025, it was decided that the defence spending of the member states should be at least 5 % of each country’s gross domestic product (GDP) by 2035. Finland supported this and will try to act accordingly. NATO has also previously agreed that at least 20 % of defence spending must be used for the procurement of defence materiel.

Finland’s integration into NATO’s common defence systems will be a long process. Defence legislation is extensive, and for decades it has been based on military non-alignment. As a result of the additional tasks caused by NATO membership, the Defence Forces will need additional personnel of about 1,500 people.