The oldest servicemen in the Second World War from all participants

[NormanStewart]

On the American side, I would say probably this man:

Sergeant, 72, Army's oldest man, re-enlists (8-9-41)

The Pittsburgh Press (August 10, 1941) SERGEANT, 72, ARMY’S OLDEST MAN, RE-ENLISTS … White-haired, erect, he hopes for chance to 'poke Hitler in nose’ … Selfridge Field, Mich. Aug. 9 (UP) – Gnarled and oaken 72-year-old Sergeant John W. Westervelt, oldest man in the United States Army, today re-enlisted for the seventh time, hoping for a chance to: …poke Hitler in the nose. Hoary-haired but erect, Sergeant Westervelt re-enlisted as a supply sergeant at the Selfridge Air Corps Base af…

If there’s anyone older than him, please let me know.