Factual error: The survivors of the Wormhoudt massacre were not picked up by the same SS soldiers who had carried out the massacre as in the series. They were picked up by a Wehrmacht ambulance unit, which is how they managed to survive to become prisoners of war.
Factual error: Captain James Lynn-Allen wasn't shot by an SS officer whilst remonstrating with him about the treatment of his men. He was shot whilst trying to escape and his sacrifice allowed another soldier to successfully escape.
Factual error: Jimmy Langley wears the single pip of a second lieutenant. He was actually a lieutenant at the time and should therefore be wearing two pips.
Factual error: Harold Alexander, although his rank of major-general is correctly mentioned by the narrator, wears the rank insignia of a full general.
Deliverance - S1-E3
Factual error: The crosses marking the graves of British soldiers outside the hospital abbreviate Private as the American "Pvt" rather than the British "Pte."