In 1949, the primary aim of the North Atlantic Treaty was to create a pact of mutual assistance to counter the risk that the Soviet Union would seek to extend its control of Eastern Europe to other parts of the continent.
Every participating country agreed that this form of solidarity was at the heart of the Treaty, effectively making Article 5 on collective defence a key component of the Alliance.
Article 5 provides that if a NATO Ally is the victim of an armed attack, each and every other member of the Alliance will consider this act of violence as an armed attack against all members and will take the actions it deems necessary to assist the Ally attacked.
“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 and consequently they agree that, if such an armed attack occurs, each of them, in exercise of the right of individual or collective self-defence recognized by Article 51 of the Charter of the United Nations, will assist the Party or Parties so attacked by taking forthwith, individually and in concert with the other Parties, such action as it deems necessary, including the use of armed force, to restore and maintain the security of the North Atlantic area.
Any such armed attack and all measures taken as a result thereof shall immediately be reported to the Security Council. Such measures shall be terminated when the Security Council has taken the measures necessary to restore and maintain international peace and security.”
The “out-of-area” debate
This article is complemented by Article 6, which stipulates:
“For the purpose of Article 5 an armed attack on one or more of the Parties is deemed to include an armed attack on the territory of any of the Parties in Europe or North America, on the Algerian departments of France², on the occupation forces of any Party in Europe, on the islands under the jurisdiction of any Parties in the North Atlantic area north of the Tropic of Cancer or on the vessels or aircraft in this area of any of the Parties. “
According to one of the drafters of the Treaty, Theodore C. Achilles, there was no doubt in anybody’s minds that NATO operations could also be conducted south of the Tropic of Cancer³. This was confirmed by foreign ministers in Reykjavik in May 2002 in the context of the fight against terrorism: “To carry out the full range of its missions, NATO must be able to field forces that can move quickly to wherever they are needed, sustain operations over distance and time, and achieve their objectives”. (Extract from the Reykjavik communiqué).
The principle of providing assistance
With the invocation of Article 5, Allies can provide any form of assistance they deem necessary to respond to a situation. This is an individual obligation on each Ally and each Ally is responsible for determining what it deems necessary in the particular circumstances.
This assistance is taken forward in concert with other Allies. It is not necessarily military and depends on the material resources of each country. It is therefore left to the judgement of each individual member country to determine how it will contribute. Each country will consult with the other members, bearing in mind that the ultimate aim is to "to restore and maintain the security of the North Atlantic area".
At the drafting of Article 5 in the late ‘40s, there was consensus on the principle of mutual assistance, but fundamental disagreement on the modalities of implementing this commitment. The European participants wanted to ensure that the United States would automatically come to their assistance should one of the signatories come under attack; the United States did not want to make such a pledge and obtained that this be reflected in the wording of Article 5.