The film footage shown below was taken after the end of the First World War and it gives an extraordinary view of the scale of the devastation and the shocking extent of the fighting across the Western Front in northern France and Belgium.
It was filmed at the beginning of 1919 with French balloon pilot Jacques Trolley de Prévaux as he flew just a hundred metres or so above the battleground. It was recently screened by the BBC.
He is shown flying over the flattened ruins of Ypres, then the flooded shell craters pockmarking the Passchendaele battlefield, the ruins of Lens where people hold a street market amid ruined buildings and, everywhere, the zigzagging trenches covering miles of country.
It was filmed by film-maker Lucien Le Saint in what is thought to be part of a French government effort to obtain reparations from the Germans for the devastation caused.
The full film is about 78 minutes long and was shown in France in the 1920s before being stored in the Musée Albert-Kahn in Boulogne-Billancourt. It was transferred into digital form in 2008 and has since been screened occasionally on French TV as En dirigeable sur les champs de bataille.
It was also used as the basis for a BBC documentary that researched the history of the film and the pilot.
A naval gunnery officer before the war started in 1914, Jacques Trolley de Prévaux had been retrained to fly the dirigibles that had been developed to spot for artillery, detect mines at sea and fight against submarines. For his actions he was awarded the Légion d'honneur and the Croix de guerre.
In the Second World War he joined the Resistance and he and his wife Lotke were shot by the Gestapo in Lyon on August 19, 1944 – as the Allies were liberating Paris.