The idea of extracting power from the wind is almost as old as civilisation itself, with records of existing windmills back as far as the 17th century BC, the time of the Babylonian emperor Hammurabi. Although mideastern countries possessed such knowledge, windmills were not introduced into Europe until the crusaders brought them back in the 13th century AD, but by the early 19th century there were 10000 windmills in operation in England alone.