There is much misunderstanding on this side of the Atlantic about the nature of NATO membership. NATO fully respects the sovereignty of each member. Unlike the EU it does not require members to do anything they do not wish to do, and has no legal powers to enforce its policies. Many Europeans think that because the Treaty says an attack on any one is also an attack on the rest the US would automatically come to their aid and fight their war for them. This faux pas has led many European countries to provide insufficiently for their own defence whilst sheltering under the US umbrella.
Article 1 favours NATO members finding peaceful means to settle disputes and warns against them using any threat of collective force in international relations that the UN would not approve. The crucial Article 3, much forgotten, urges each member to build up their own individual defence capacity.
Article 3
“In order more effectively to achieve the objectives of this Treaty, the Parties, separately and jointly, by means of continuous and effective self-help and mutual aid, will maintain and develop their individual and collective capacity to resist armed attack.”
The better known Article 5 does indeed says an attack on one is an attack on all, but it goes on to make clear that does not require all to respond by declaring war on the aggressor and joining the battles.
Article 5
“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 recognised 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 .”
In other words whilst NATO can ask each nation to join in a war, each state can decide instead to simply issue a condemnatory statement, impose sanctions, or seek diplomatic redress as it sees fit.
With the US spending around two thirds of NATO’s budget and supplying a higher proportion of the fighting resources the other members are right to be concerned about committing NATO to any action where the US may decide to exercise its right not to contribute. The European members are now increasing their spend . President Trump has been insisting that European members of NATO make a much enlarged contribution to their own defence, as he wishes the US to be less committed to the defence of Europe. So far most of the countries have not made much increase in their capabilities and are very dependent on US heavy lift, air cover, missile protection and the rest. President Trump thinks they need to be spending 5% of the their GDP on defence whilst most have only just got to 2%.
I will consider tomorrow whether the UK should be willing to shoot down a Russian plane. The context for the decision should be a cautious approach as Poland, Germany and the other eastern members of NATO are much better placed to respond to daily testing of the eastern borders of NATO adjacent to Russia. It would be more normal to intercept and conduct the Russian plane out of the area. The UK should concentrate on using its current resources to respond to any Russian drone/missile or aircraft intrusion into our airspace which we are much better placed to do from our own airfields and installations. Our usual practice is to intercept and conduct Russian planes out of our airspace promptly, which is a measured response.