The film is based around the fictionalised events of a massacre of 26 US soldiers known as "Operation Sonnenblume (Sunflower)", when in fact the actual Operation Sonnenblume happened in North Africa in 1941. In August 1944, Mortain - the village with the sunflower farm referred to in the episode - was an important battle site within the wider Normandy Campaign and the eventual Falaise Pocket, but the incident bears similarity with the later Malmedy massacre. In the show, the Americans also attempt to pressure MI5 into handing over Strasser by threatening the 1943 BRUSA Agreement and loan terms the US has extended the UK.