Early in WW2 in support of Japan there were Germans, in axis with the Italian navy, who operated submarines in the Pacific, Atlantic, and Indian Ocean.

The group that operated primarily in the Pacific was called the "Monsun Group" which was composed of 41 U-boats bound for Penang Malaysia. These were various missions from 1943 to 1945. A large number of these were lost while traversing Allied held areas, and only a small fraction ended up making return trips to Europe. Penang was previously a British operated seaplane base until the Japanese military took the territory around February of 1942. The German and Italian submarines started to show up in early 1943. This was also the only Navy base operated by all three members of the Axis.

At the time they often hunted in groups with Japanese submarines - but were most often used as cargo ferries for supplies and technical data from Germany to Japan. During this period, travelling back and forth between Germany and Japan, combined both countries caused considerable damage to the Allied shipping routes. Possibly sinking around 200,000 tons. Once the Allies broke the Enigma code they ended up taking considerable losses to the combined submarine forces.

By March of 1944 the base started getting low on supplies and the threat of sea power by the Allied forces in the Pacific started to cause concern for the Axis powers. The Japanese withdrew their submarines from the base before the end of 1944 because Penang had fallen within bombing range of the Allied forces. The Germans held their position until December of 1944 before withdrawing to a former British shipyard in Singapore.

When Germany surrendered in the European theater the remaining submarines in the Pacific theater were taken by the Japanese and the sailors where moved to Batu Pahat. The last submarine of the German fleet, U-234, left Germany with two Japanese officers, a ME-262 fighter jet, and other precious war materials but the war had ended for them before they even got out of the north Atlantic. The commander of that submarine surrender in Portsmouth, NH USA at the naval yard. The Japanese officers on board committed suicide.