For Kapitaen zur See and Fuehrer der U-boote Karl Doenitz the outbreak of war between Germany and the United Kingdom in September 1939 found the submarine arm of the Kriegsmarine unready for conflict. Nevertheless, Doenitz's 'Grey Wolves' were still able to inflict substantial losses on vessels carrying Britain's lifeblood. The conflict widened after the occupation of France and its ports gave the submarines direct access to the Atlantic shipping lanes, which in turn led later to a larger arena. This program depicts the course of the U-boat war in its initial phase in vivid images captured primarily by German cameramen with much being presented to the viewer for the first time.