The claim of Japanese involvement, specifically a submarine operating with "Kormoran", is based on several elements. The German survivors were found with milk bottles bearing Japanese labels. Although cited as evidence that a Japanese submarine was supplying "Kormoran", the bottles were obtained from the supply ship "Kulmerland", which had taken on supplies in Japan. Sketches drawn by one of the interned Germans were believed to contain an account of the battle in the "Deutsche Einheitskurzschrift" shorthand system. A civilian working for Australian military intelligence attempted to decode these, and after relying on interpolation and speculation to make sense of the decoded characters and fill in the gaps, came up with a message that included the phrase "a Japanese gunfire attack from Japan itself". However, several shorthand experts consulted by Winter could find nothing resembling "Einheitskurzschrift" (or any other shorthand style) in the sketches.