Four German soldiers in bunk beds who had been woken up for a surprise photograph during World War I; ca. 1917.
I think it’s worth noting that the photo captured the men with their eyes closed because the method of illumination was a flash-lamp, which burned a bit of magnesium in a trough held up by the photographer. That light source burnt long enough for the men to react to it before the shutter was tripped on the camera, thus their eyes are closed.
Today if you were to take this photo with a digital camera and flash, you might capture them with eyes open, since the time between flash and shutter is much smaller and more instantaneous of an image capture.