If ever there was an ultimate weapon of war, it would have to be the nuclear submarine. For more than 60 years, ballistic missile-armed submarines have prowled the world’s oceans, ready to unleash nuclear armageddon at a moment’s notice. Meanwhile, fast attack boats track and stalk the missile-armed ‘boomers’, the two rivals locked in a shadowy game of cat-and-mouse deep beneath the waves. But while nuclear deterrence is the modern submarine’s most famous mission, it is far from the only one. Throughout the Cold War and into the present day, these vessels have served as the eyes and ears of the Navy, using stealth and guile to perform covert reconnaissance of enemy shores. And perhaps the most daring and successful such feat of naval espionage took place in the early 1970s, when a U.S. Navy submarine snuck into a Soviet naval base to tap an underwater communications cable. This is the extraordinary story of Operation Ivy Bells.