Israel launched blistering attacks on the heart of Iran’s nuclear and military structure on Friday, deploying warplanes and drones previously smuggled into the country to assault key facilities and kill top generals and scientists — a barrage it said was necessary before its adversary got any closer to building an atomic weapon.

Iran retaliated by unleashing scores of ballistic missiles on Israel, where explosions flared in the skies over Jerusalem and Tel Aviv and shook the buildings below.