I have been studying the role of Imperial Japan in World War II and currently I am researching the relations between the Axis Powers. I have thus far read that especially Germany showed interest in Japan's proposal to jointly attack the Soviet Union. This plan was in the end never fully carried out, due to the fact that Germany delayed it's plans for invading the Soviet Union and Japan showing more interests in conquering parts of Southeast-Asia and the Pacific. But I was wondering if, aside of the joint attack on the Soviet Union and various cultural exchanges, there would be any other cooperation between especiially germany and Japan but perhaops also Italy and Japan?
The level of military cooperation between the European Axis powers and Japan was relatively minimal. The only truly cooperative military ventures that managed to translate from paper projects to an actual military operations were blockade-running and a wolfpack of U-boats operating in the Indian Ocean (Monsun Gruppe).
Initially, individual surface ships would make blockade runs carrying supplies that neither side could produce in their home areas. The height of surface blockade-running was between April 1941 and May 1942. Some of these supplies had strategic value like Asian tungsten and rubber or plans for German radars and antiaircraft guns, but others less so. Tea, cocoa, peppers, and vegetable oils counted among the cargo manifests of goods sent to Europe; while these items were in short supply, the tenuous nature of the the supply line necessitated a much more strategic mentality. Allied naval superiority grew to an extent that the Axis abandoned surface blockade running for submarines from 1942 onwards.
The Monsun Gruppe (and its Italian counterpart the Merkatur boats) grew out of these endeavors, building upon earlier Japanese proposals to base U-boats in the Indian Ocean in Japanese-occupied Southeast Asia. Overall, these operations were a disappointment as Allied ships sank many of the assigned Monsun U-boats en route and those that did make it found that tropical weather played havoc on German equipment.
In hindsight, the Axis alliance was highly self-serving and characterized by miscommunications on both sides. The Germans deeply underestimated the extent to which the Japanese considered their non-aggression treaty with the USSR sacrosanct. The Japanese government also overestimated German military effectiveness and never built up a trusting relationship with its German and Italian military attaches.
Sources
Elleman, Bruce A., and S. C. M. Paine. Naval Blockades and Seapower: Strategies and Counter-Strategies, 1805-2005. London: Routledge, 2006.
Krug, Hans-Joachim. Reluctant Allies: German-Japanese Naval Relations in World War II. Annapolis, Md: Naval Inst. Press, 2001.
Millett, Allan Reed, and Williamson Murray. Military Effectiveness. Vol. 3, Vol. 3. Cambridge: Cambridge University Press, 2010.