The Heinkel He-111 was the mainstay of the German offensive against Great Britain during the Battle of Britain It was produced in far larger quantities than the Do-17 series & remained in service throughout the war The Heinkel He-111 was first displayed in January 1936 not as a bomber but in the guise of a civil airliner In 1937 the civil disguise of the He-111 was abandoned He-111 B-1s were sent to the Condor Legion fighting in the Spanish Civil war The success of the He-111 in Spain played a large part in shaping German bombing policy which later proved wrong when the lightly armed bombers suffered heavy losses over Britain when opposed by modern & determined fighters The He-111 H-series was by far the most important variant of the bomber the H-20 being the first to carry a dorsal gun turret & enhanced armament together with a redesigned nose & more powerful engines