NATO is a promise, and now it's broken.The big picture: The alliance was built on the premise that an attack on one member is an attack on all. President Trump has made that conditional: if you won't help me in my war, I might not show up for yours.NATO's mutual defensive framework doesn't actually apply in the case of Iran, a war taking place far from the alliance's territory. But it could be the death knell for the most powerful and consequential alliance of the past eight decades.Driving the...