My knowledge of the Japanese involvement in WWI is minimal but I know they were mostly a diplomatic ally rather than a provision of force for the West. I want to know if Japanese and American soldiers ever fought in the trenches side by side during this war?
The extent of Japanese Army ground operations were limited to the Far East. This thread by myself and /u/thefourthmaninaboat goes into more details on Japan during the war, but at no point were Japanese soldiers deployed on the Western Front, either prior to the US arrival or during.