I am studying the relationship between canon performance and armor penetration in regards to battleships. I have identified a couple of problems in obtaining reliable data and published opinions on this subject. For some reason western, based outside of Europe, authors tend to publish data & opinions that Weighted in some degree towards views more based on wartime propaganda than actual evidence.
One example is the armor type of upper belt area of the Bismarck; Was it Wh or Kcna ?
Video evidence supports Wh at the shell damage locations. trouble is the same video evidence of the wreck suggests that the Kcna armor of the forward conning tower reacted more like homogeneous armor than face hardened armor ( relative smooth curved entry crater opposed to the more usual fractured crater created in Kcna type armor when penetrated ).
So question one is 'which type of armor was used in upper belt and has any one else noticed the shape of the penetrating hits on the Bismarck suggest a different result than shown in testing on Kc armor plate?
The second part is to do with canon development between Japan & Germany. Is there any evidence of exchanges of information in this area. I have read accounts of design exchanges during the war of airplane tech, submarine tech and radar equipment, and I am wondering if any exchanges occurred before the war?