Israel launched a sweeping assault on the heart of Iran's nuclear and military structure Friday, deploying warplanes and drones previously smuggled into the country to strike key facilities and kill top generals and scientists in a barrage it said was necessary before its Iran got any closer to building an atomic weapon. Iran retaliated late Friday by unleashing scores of ballistic missiles on Israel, where explosions flared in the skies over Jerusalem and Tel Aviv and shook the buildings below.