By the outbreak of World War II, Germany had done much to replace the Kaiser's High Seas Fleet, which was scuttled following the German surrender at the end of World War I.

Forced to build her fleet anew, although small, the Kriegsmarine possessed some of the most modern and technically innovative warships in existence. Although the heavy units of the fleet were too small in number to pose much of a threat to huge fleets such as the Royal Navy, Germany was particularly well served by her Navy's smaller vessels, in particular two specific branches - the U-Boats and the S-Boats.

Known to the allies as the E-Boats (E being indicative of 'Enemy'), they performed sterling duties in both the Black Sea and the English Channel, where they became a particular scourge. Their achievements can also be gauged by the high number of successful commanders who were decorated with the Knight's Cross of the Iron Cross, in recognition of the tonnage they had sunk.