Sous le Manteau (literally Under the Cloak; usually translated as Clandestinely) is a French documentary consisting of footage shot clandestinely by French officers held during World War II in Oflag XVII-A, a POW camp in northeastern Austria.

Oflag XVII-A was a prisoner-of-war camp operated by Nazi Germany in Austria, on the border of Czechoslovakia. Its 40 barracks housed five thousand French prisoners of war captured during the Battle of France.^[1] According to Robert Christophe, in his making-of booklet on the film, Oflag XVII-A had a Gaullist resistance group called "La Maffia", which had ties to a French Resistance group (apparently the only such collaboration between prisoners outside France and resistance inside it), and thus acquired the materials for the camera (and supplies for escape attempts).^[2]

Taking advantage of humanitarian packages from France, the prisoners smuggled in materials necessary for the construction and operation of a camera. Film was sent from France in packets with food for prisoners; they were hidden in sausages and other foods,^[3] and after being developed the negatives were hidden in the heels of the prisoners' boots (the footage documents such detail). Fourteen rolls were filmed by March 1945.^[3] The camera was made from a wooden box, which was hidden in a Larousse dictionary;^[3] the spine of this dictionary was capable of being opened like a shutter.^[1]

The 30-minute film documents daily life in the camp, including a theater production, food distribution, as well as a surprise raid by the Nazi guards. The film even documents the digging of tunnels for several escape attempts.^[4] One, of which parts are documented in the film, resulted in 132 prisoners escaping; only two made it back to France.^[5]

After the camp was liberated by the Soviets the rolls were hidden in a mess tin and given to the French liaison officer for General Jean de Lattre de Tassigny. A booklet by Christopher about the making of the film was published in 1948 by Éditions OPTA.^[3][6] Sous le Manteau has been distributed by Armor Films, with commentary by Maurice Renault and Robert Christophe.^[7]

The BBC's Christian Fraser described it as "so professional ... that on first viewing you would be forgiven for thinking it is a post-war reconstruction."^[1]