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For decades, Britain and America's Cold War submarines waged a secret war of espionage against the Soviet navy. Deep in the ocean, crews were locked in a game of cat and mouse as each side battled to gain the tactical and technological advantage.

Throughout the 1970s and 80s, the front line of the Cold War was hidden beneath the ocean. Submariners from three navies - American, Soviet and British - played a deadly game of cat and mouse in a secret war of espionage and intimidation. The nuclear balance between East and West was constantly shifting.