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In WWII there were OSS and SOE operations even within Germany but no direct action operations were carried out against Japan. Granted it was harder to impersonate Japanese subjects, but surely it was not impossible given the large numbers of Japanese in America and perhaps Chinese and Korean recruits who had lived in Japan.
They would be able to infiltrate and sabotage Japanese factories and depots much the way the Germans blew up factories in America during the First World War. This would provide at least a means of striking at the Japanese industrial machine that was not possible until late into the war.