Introduction
Germany and Japan maintained communication and exchanged personnel during the Second World War because both regimes saw strategic value in cooperation, even though their war aims and theatres were very different. Their early alignment grew out of the Anti‑Comintern Pact of 1936, which bound them in shared hostility toward the Soviet Union and international communism. This ideological overlap created a basis for military and intelligence exchanges, including sharing assessments of Soviet forces and exploring clandestine operations against the USSR.
How did Japan and Germany cooperate?
Practical cooperation deepened after 1937–40 as both powers sought to strengthen their military capabilities. Japan sent officers such as General Tomoyuki Yamashita to Germany to study modern warfare, inspect German units, and acquire advanced technology. Germany, in turn, provided technical assistance in aircraft and submarine design, while both sides exchanged strategic materials and specialists through long‑range submarine missions under the Yanagi program. These missions also carried gold, industrial goods, and high‑value passengers, reflecting the logistical and technological interdependence that developed despite vast geographic separation.
An evolving relationship.
However, this cooperation was never seamless. Even before 1941, German–Japanese relations were marked by mistrust, conflicting priorities, and uneven willingness to share sensitive technologies. Japan’s war in China conflicted with German interests, and Hitler’s racial ideology made him ambivalent about close partnership with Japan. Still, shared opposition to the United States eventually pushed both powers into the Tripartite Pact of 1940, formalizing their alliance.
Everything changed dramatically in August 1939, when Germany signed the German–Soviet Non‑Aggression Pact. Japan, which had been fighting the USSR along the Manchurian border, was outraged and renounced the Anti‑Comintern Pact soon afterward. The German–Soviet agreement shattered the ideological foundation of German–Japanese cooperation and forced Tokyo to reconsider its strategic position. Japan subsequently signed its own neutrality pact with the USSR in 1941, distancing itself from Berlin’s anti‑Soviet agenda.
When Germany violated the pact by invading the Soviet Union in June 1941, the relationship shifted again. Berlin hoped Japan would attack the USSR from the east, but Tokyo—still recovering from earlier defeats by Soviet forces—refused. Instead, Japan focused on its southern expansion and war with the United States. From this point onward, German–Japanese cooperation became symbolic rather than strategic: exchanges of personnel and technology continued, but the two powers fought fundamentally separate wars with diverging priorities and no coordinated grand strategy.
Setting the stage.
Although there was a requirement for technology exchange, the underlying relationship between Germany and Japan was flawed. This sets the stage for the discussion of the possibility of trans polar flights between Germany and Japan. As aircraft with suitable performance envelopes became available, were they used to suplement or in some cases replace the submarine traffic between the two nations.