The power of German 37mm AA!
 

How german raider sank H.M.A.S Sydney.http://www.theage.com.au/national/ge...0914-4gb3.html

Armament: 6 x 150 millimetres (5.9 in) guns (hidden behind counter-balanced covers[2]), 2 x 37 mm anti-tank guns, 5 x 20 mm FlaK anti-aircraft guns, 2 x twin 533 mm (21 inch) torpedo batteries above the waterline; two single tubes below, 390 mines

Thanks for the armarment specs of the kormoran,from what i understand though they only had enough time too get a few rounds off from the 37mm AA and managed to let a torpedo go, which caused the most damage.