Clarence E Allen was declared missing in action on 12 October 1944, aged 23. Allen was taking part in a dive-bombing mission over Aachen, when his squadron engaged enemy fighters over Dusseldorf. All aircraft except Allen's returned to base, and eyewitnesses suggested that his aircraft was crashed near the site of the air battle.



Allen's remains were recovered by the American Graves Registration Command in 1948, but they were deemed unidentifiable, and he was interred at Ardennes American Cemetery, as an unknown soldier. While his name was listed on the Wall of the Missing at Netherlands American Cemetery.



Following the excavation of his crash site in Germany 2003, and the identification of his aircraft, Allen was disinterred from Ardennes American Cemetery in 2005 and positively identified in 2018. His remains were returned to his family.