In 1940, 5,000 French officers were held as prisoners of war in a German camp called Oflag 17A. There were thousands of captive soldiers in similar camps all across Germany, but these inmates had an advantage other prisoners could only dream of: a secret camera, smuggled in from the outside world. The footage—and their story—is incredible.

The grainy video above is an excerpt from Sous Le Manteau (Under the Overcoat), the top-secret, seldom seen documentary shot by the prisoners of Ofla 17A themselves. It documents their repeated attempts at escape over a five-year period. But how did they have a camera in the first place? And why were they never found out?

How the Sausage Is Made

As you might expect, the men behind Sous Le Manteau went through great lengths to obtain their video camera; sneaking something into a tightly guarded prison camp is nearly as hard as sneaking something out. Fortunately, these were some incredibly clever captives.

According to the BBC, the camera was smuggled into the camp as individual pieces, which they later assembled into a functional device. And they did it by shoving those pieces inside of sausages.

But even that wasn't quite enough; the camp's German guards routinely checked food for contraband by slicing random links down the middle, so the smugglers had to carefully place the components in the very ends.

The difficulty didn't stop there; even once the (sausage-scented) camera was inside, it still had to be carefully hidden. The prisoners-cum-cameramen built the device into a hollow dictionary, with a spine that opened up to reveal the hidden lens.

The Astonishing Tale of Nazi Prisoners, a Smuggled Camera, and SurvivalS

This crazy, covert contraption not only to let them keep their secret from German guards, but to film the camp's day-to-day activities with a staggering amount of freedom. All it would have taken to be found out was an intellectually curious guard. Fortunately, it seems that none of them was.

The Great Escape

Over a matter of years, the prisoners filmed 30 full minutes of footage on 14 reels of 8mm film, capturing everything from mundane yard activity to clips of performances in the camp's makeshift open-air theatre. But perhaps the camera's greatest task was filming the construction of dozens of escape tunnels that the prisoners built in various bids to free themselves.

The Astonishing Tale of Nazi Prisoners, a Smuggled Camera, and SurvivalS

After a dogged 32 attempts, the tunnel system finally led to a 132-man breakout that heightened prison security across Germany, and set the stage for the Stalag Luft III breakout, of The Great Escape fame.

Amazingly enough, the inmates of Oflag 17A weren't the only POWs who managed to capture their captivity on film. Worlds away, a marine named Terence Sumner Kirk, took shots of Fukuoko No. 3 prison in Japan on an improvised pin-hole camera, burying the resulting photos in the latrine for safe keeping.

A makeshift POW camp camera can't exactly hold a candle to any real spy camera in terms of sophistication, but it's flat-out amazing that anyone could build any kind of functioning camera in those circumstances, much less one that was covert and worked. And the footage, while rare and understandably slightly frenetic, is a staggering accomplishment of ingenuity.

In short, it's a miracle that this footage was ever taken in the first place, much less that it still exists for us to appreciate today. [Video courtesy d'Arte Les Mercredis de l'Histoire via Eric Gross, h/t BBC]