The Office of Naval Intelligence (ONI) prepared nearly fifty booklets, or serials, of intelligence gathered during the course of anti-submarine operations throughout multiple theaters in World War Two. The intelligence booklets were prepared from material obtained through the capture or sinking of enemy submarines, interrogations of prisoners, diaries obtained from the dead, and other methods. These booklets were considered confidential and classified and secret at the time of publication in order to safeguard sources. This information has since been declassified. This is the second of a four volume series.