img_7373 December 7, 2016 3024 × 4032 Oscarsborg Fortress Pictured is Aaron, complete with battle scars inflicted by Nazi planes that attacked the fort a few hours after the sinking of the Blücher. The gun is a German-made 28-cm (11-inch) calibre Krupps that fires 255 kg (562 lb) high-explosive shells.