Kristersson is one of the hundreds of politicians, diplomats, security officials, and arms dealers gathering at the Munich Security Conference this weekend to consider the end of a period of unrivaled American power. In the new era, European leaders are not only promising to take more responsibility for the conventional defense of their continent; they’re also beginning to talk about an expanded nuclear deterrent of their own. Practically, this would mean leveraging the capabilities of Britain and France, currently the only two European states with nuclear weapons.