Hi Aaron, try and obtain the book 'Reluctant allies' ISBN 1-86176-195-3 (2001), which give a clear insight to the question you ask. The book title as suggests there was not a great deal of co-operation between the two navies, at all levels. It was Hitler who mainly instigated the Japanese to obtain knowledge of German U-boat construction, by ordering the transfer/sale of a few U-boats to Japan, as well as allowing Japanese naval personnel access to German technology when they came on the few occasions to the Biscay Bases. But in the Indian Ocean, in general the German operations being limited to the western side, with Japanese submarines operating in the east and Australian waters. Except for the few U-boats in transit to Japan held bases, which would attack enemy shipping happened upon while en-route and when they returned. The two navies generally kept their offensive operations secret, except, presummably when friendly boats were passing through the others operational areas. Regards john