In the waning days of May 1959, as Cold War tensions simmered just beneath the waves of the North Atlantic, a diesel-powered submarine from the United States Navy quietly made history. The USS Grenadier, a Tench-class submarine commissioned after the Second World War and still active in the early nuclear age, was patrolling a particularly sensitive patch of ocean near the Greenland-Iceland-United Kingdom gap. This was no ordinary patrol. Intelligence analysts had begun to suspect that the Soviets were pushing their submarine forces westward, probing closer to NATO territory than ever before. For Admiral Jerauld Wright, the Commander in Chief of the Atlantic Fleet, it was a moment of opportunity wrapped in paranoia. He had issued an informal challenge to his undersea commanders: the first one to produce hard evidence of a Soviet submarine prowling the Atlantic would earn a case of Jack Daniels.