Douglas MacArthur accepted Japan’s surrender and signed first for the Allied powers aboard USS Missouri.
MacArthur served as Supreme Commander for the Allied Powers and presided over the surrender ceremony in Tokyo Bay. After the two Japanese representatives signed, he signed the instrument on behalf of the Allied powers.
His role reflected his command authority over the occupation and the wider Allied arrangement in the Pacific. Fleet Admiral Chester Nimitz signed immediately afterward as the United States representative.
MacArthur is sometimes confused with Nimitz because both were senior American commanders in the Pacific. Nimitz represented the United States, while MacArthur signed in his broader role as Supreme Commander for the Allied Powers.