Before Israel launched an unprecedented wave of strikes against Iran’s nuclear facilities and top military leaders this week, its spies were already on the ground in enemy territory. Israeli intelligence agency Mossad had smuggled weapons into Iran ahead of the strikes,

Iran confirmed Friday evening local time that it had fired “hundreds of various ballistic missiles” towards Israel, in what it called the “beginning” of its “crushing response.”

Israel asserted the barrage was necessary before Iran got any closer to building an atomic weapon, although experts and the U.S. government have assessed that Tehran was not actively working on such a...