A new Smithsonian Channel series will chart the stealthy game of undersea warfare from the greatest submarine campaigns of World War II. It profiles the strategic masterminds behind the brutal tactics of Nazi U-boats and reveals the extraordinary feats of Allied subs in the Atlantic and Pacific. Both the Axis and Allies employed unrestricted submarine warfare to bring their enemies to their knees in World War II. Submariners on both sides were a special breed of warrior, always volunteers, often fighting alone. Sub warfare evolved rapidly during the war, as German U-Boats and American submarines attacked military targets and commercial shipping. Submarine attacks created chaos and unnerved adversaries. And while the world's oceans provided concealment and protection, the environment was unforgiving. Each hour-long episode of Hell Below features expert analysis and stock footage along with dramatic re-enactments filmed aboard authentic World War II era submarines, placing viewers in the heart of the action.