Tasks 

NATO’s purpose is to defend the freedom and security of its member states through civilian and military means.

NATO is the embodiment of the transatlantic relationship through which the security of North America is durably linked to the security of Europe. It is a practical expression of the support member states provide to their mutual interests through effective and collective efforts

The fulfilment of NATO’s security policy is being helped by the following means:

• maintaining adequate military capabilities in order to prevent war, i.e. for the effective defence of member states. 
• comprehensive capabilities to manage crises affecting the security of the member states, 
• maintaining a dialogue with partner countries with a view to enhancing security in Europe.

Collective security is referred to in Article 5 of the North Atlantic Treaty, which states that the Parties agree that an armed attack against one or more of them in Europe or North America shall be considered an attack against them all.