During the 1990-91 Gulf War, global media was swamped with images of live combat. New technology allowed the world to see photographs and films of night-time bombing raids. This image-intensifying technology, developed specifically for military use, fascinated Ruff and inspired him to create the Nights series.

The night vision device Ruff used amplifies available light sources and gives the image a green hue. Once again Dusseldorf became his source material and he began to photograph alleys and backyards, making visible parts of the city otherwise unseen or overlooked. Pleased with the unnerving and ghostly images that resulted, Ruff soon extended his night-time studies to other cities. These works were first presented at the documenta IX exhibition in 1992.