[1] Their great-grandfather and grandfather had been army officers, and their father was a general, Ernst Freiherr von Forstner (1869–1950), who had won the Pour le Mérite with cluster as a regimental commander during World War I.

[1] Siegfried von Forstner joined the Kriegsmarine in 1930 and served for four years on the German cruiser Nürnberg following training as an artillery technical officer.

Baron von Forstner sank two ships during a submerged daylight attack on convoy SC 129 before U-402 was depth charged and damaged by the corvette Gentian.

[6] Von Forstner and his wife saved their home in Hamburg from burning during August, 1943, air-raids by staying on the roof and extinguishing incendiary bombs.

[9] A U-boat believed by the Allied Anti-Submarine Assessment Committee to be U-402 was sunk with all hands on 13 October 1943 by a Mark 24 FIDO Torpedo dropped by Grumman TBF Avenger aircraft from USS Card.