Short answers, pulled from the story.
The North Atlantic Treaty Organization began on the 4th of April 1949 when twelve nations signed the Washington Treaty. The original founding members included Belgium, Canada, Denmark, France, Iceland, Italy, Luxembourg, the Netherlands, Norway, Portugal, the United Kingdom, and the United States.
Most nations added between 1990 and 2024 were former Warsaw Pact states or territories of the former Yugoslavia. Finland joined on the 4th of April 2023 and Sweden followed on the 7th of March 2024 to complete the current roster of thirty-two countries.
Article 6 limits the geographic scope of defense guarantees to islands north of the Tropic of Cancer including North American and European mainlands. An attack on Hawaii or Puerto Rico would not trigger an Article 5 response because these locations fall outside the defined boundaries.
Most member states failed to meet their commitment to spend at least two percent of their Gross Domestic Product on defense in 2023. Poland leads the list with a contribution of four point twelve percent of its GDP while Iceland spends only three hundredths of a percent.
Denmark, Iceland, and Norway agreed there would be no permanent peacetime bases on their soil and prohibited nuclear warheads unless explicitly invited by their governments. Denmark made an exception for Thule Air Base which is now known as Pituffik Space Base located in Greenland.