https://www.msn.com/en-us/news/world/why-are-nato-articles-4-and-5-being-discussed-after-the-blast-in-poland/ar-AA149uhb?ocid=Peregrine&cvid=a9cfeee963294e7fa382962c9fda1823
Article 4 of the NATO charter says that member states “will consult together whenever, in the opinion of any of them, the territorial integrity, political independence or security” of another member is threatened.
It establishes a consultation mechanism among members, “to exchange views and information, and discuss issues prior to reaching agreement and taking action,” according to an explanation on the NATO website. “It also gives NATO an active role in preventive diplomacy by providing the means to help avoid military conflict.”
The primary forum for such discussions is the North Atlantic Council, the alliance’s political decision-making body.
Article 4 has been invoked seven times since NATO was established in 1949. Most recently, Latvia, Lithuania, Poland, Bulgaria, the Czech Republic, Estonia, Romania and Slovakia used it to hold meetings following Russia’s invasion of Ukraine.
Member states are not obligated to act if Article 4 is invoked, although deliberations could result in a decision to take joint NATO action