The Captain of a U-boat was responsible for all actions onboard his vessel and was required to be total familiar with every system on the submarine.  The captain was the senior commander onboard and often personally conducted torpedo attacks against enemy vessels, providing enemy vessel data to the weapons and torpedo divisions in order to successfully engage an enemy target.  Most submarine commanders were in their mid to late 20s and held the rank of either Oberleutnant zur See or Kapitänleutnant.