Allies appear to duck and cover as Trump threatens Canada and Greenland

Whenever we talk about NATO it's usually in the context of money — or the famous all-for-one, one-for-all treaty clause known as Article 5.

The provision is the bedrock of the Western military alliance, allowing leaders from Latvia to London to Ottawa to sleep better at night knowing more than two dozen other like-minded nations have their backs.

What often doesn't get much attention is the preceding paragraph: Article 4.

European defence experts sometimes call it the "neglected younger sibling" of the alliance. The provision commits NATO members to "consult together whenever, in the opinion of any of them, the territorial integrity, political independence or security of any of the parties is threatened."