How do you blast a hole through a mountain of concrete and granite and then blow up what hides beneath it―all without crossing the nuclear line? Since the Israel-Iran conflict broke out last week, much speculation has centered on this weapon: the GBU-57/B,

Israel's plan to destroy Iran's nuclear sites has run into trouble at Fordo — a site buried so deep underground that only US B-2 bombers might be able to hit it.