There's a concept in Islamic tradition that divides the world in two: the 'realm of Islam,' where Muslims are meant to rule, and the 'realm of war' — everywhere else, territory that, in the most hardline reading, is legitimately open to conquest and violence until it's brought under Islamic rule. Al-Qaeda took the hardest possible version of this: American civilians weren't off-limits on 9/11, they were the target — precisely because they were civilians in the 'realm of war.'

Almost nobody in the US knew this framework existed before 9/11. What's more surprising is that twenty-five years later, most people still don't — it barely comes up in schools, the news, or even most academic discussion of the attacks. The official 9/11 museum's own explanation of why the attacks happened runs to a few sentences, with almost no sourcing.

That gap matters. If you don't understand the worldview that treats you as a legitimate target simply for existing outside a certain religious-political order, you can't make sense of the pattern of who gets attacked, or why. This day lays out that vocabulary plainly, so the rest of the month's stories have context.