NATO is a defensive pact, with no further obligations

From the director of global policy at GW Bush Institute ... [fear not dems, it is accurate, no lie]

NATO is the gold standard in international alliances, enhancing, supporting and advancing U.S. national security like no other partnership. Created in 1949 with the United States as a founding member, NATO is a defensive alliance committed to collective defense, crisis management, and deterrence. 
https://www.bushcenter.org/publications/nato-has-invoked-article-5-only-once-in-its-history

The alliance’s commitment to Article 5 – NATO’s collective defense agreement that means an attack against one shall be considered an attack against all – is the core  of NATO’s existence, evolution, and unparalleled  strength. The only time it has been triggered was after Sept. 11, 2001, when NATO  aircraft were deployed to help protect U.S. airspace after terrorists murdered thousands of Americans in New York City, in the crash in Pennsylvania  and  at the Pentagon.
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Trump is apparently trying to spin it that Iran was on the verge of attacking, so NATO should be obliged to assist USA against Iranian aggression. At least most all are not falling for his twisted reasoning and deception.
He is also trying his pathetic best to crawl out an escape hatch, claiming, paraphrased, that 'nobody told me about the strait of Hermuz'.
If a NATO member attacks another country, other NATO members are under no obligation to join the conflict.