Winston Churchill said the only thing that frightened him during World War II was the U-boat peril, and for good reason. A mere 15 months into the war, fleets of the German subs, known as "wolfpacks," sink 2.5 million tons of shipping supplies from Canada, nearly starving Britain into submission. Surrender would mean Europe now belonged to Hitler. Relive these early days of this Atlantic struggle through the harrowing stories of German and British soldiers, and witness it all via stirring reenactments and explosive archival war footage.

"Wolfpacks," teams of German U-boats that attack at night, are sinking convoys of allied ships along with Britain's hopes of ever controlling the Atlantic. However, the development of radar allows escort warships to lock in on U-boats ten miles away. This new technology, plus the lucky discovery of German codebooks and equipment, gives Britain the upper hand, but the triumph is short-lived. Hitler orders the mass production of U-boats and the carnage continues. Britain needs America's help, and thanks to the Japanese, their wish comes true.

Pearl Harbor changes the Battle of the Atlantic forever. Both sides have what they want: England and Canada have their American ally and German Commander Karl Donitz will soon have 300 U-boats ready to stalk the oceans. The goals are the same, but the battlefield is about to change. The "Convoy War" is set to engulf the Eastern seaboard of the U.S. and Donitz is about to teach the U.S. Navy a painful lesson in the art of submarine warfare. Witness it all through vivid battle footage, reenactments and witness testimony from allies and enemies.

It's 1943 and German U-boats continue to decimate allied shipping. The allies must find a way to defeat Admiral Karl Donitz's "wolfpack" or they will lose the war. The stakes have never been higher, the battles have never been larger and the casualties have never been higher. By the time World War II ends, no other branch of the armed forces will suffer as a high a mortality rate. Hear the stories from the German and allied soldiers, who still carry with them the haunting memories of the Battle of the Atlantic.