During the second world war, the United States and its allies were struggling to find a code by which to communicate across the Pacific Ocean - one that could not be broken by the Japanese enemy. The solution cam in the form of the Navajo people, whose language was as elusive as it was complex. Through their incredible linguistic skills, the Allied forces were able to convey life-or-death information to on another - information that, in some cases, altered the very course of the war. In this eye-opening documentary, renowned historians and several Navajo veterans relate how a mere handful of WWII marines devised the only unbreakable code in modern military history.