Trump hit out at our Nato allies in various ways over the last week. However, the most direct indication that he would like to abrogate US commitments under the North Atlantic Treaty was this:
https://youtu.be/MDkUvVgKBqI?t=1684
Listen a couple of times, and consider what he was saying. It boils down to:
- Montenegro is an aggressive country;
- maybe, Montenegro will start a war;
- if they did, this would commit the US into joining them in that war, thus resulting in WW3.
The argument is ridiculous on many fronts, but is a clear indication (not the first) that Trump wants to abrogate Article 5 of the treaty, which reads:
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 .
This is the most important article of the whole treaty, and the biggest deterrent to Russia against armed intervention in Nato countries. Montenegro was desperate to get Nato protection, as Russia has been trying to gain control there, including via
an attempted coup. I think withdrawal from Nato by the US is Putin's ultimate wet dream.
I would note that Trump generated concern at the 2017 Nato summit by changing his prepared speech (agreed with his key intelligence, defense and state department heads) omitting recommitment of the US to Article 5. The most rational explanation for this is that Trump wants to kill Nato, but (unlike the Paris Climate Agreement, Iran Joint Comprehensive Plan of Action, Trans Pacific Partnership and Transatlantic Trade and Investment Partnership with the EU) cannot easily achieve this in the short term. Remember that Trump declared Nato "obsolete" during the 2016 election campaign.