During the World Wars there used to be a complete power cut in the United Kingdom and many other countries. These power cuts were so intense that even in the night there was no electricity, which used to make it very difficult for the German bombers to spot their bombing sites and the other residential areas. Such an intense power cut during the war time is known as "Blackouts".

Other blackout was that the residents had to paint their windows complete black so that no light could escape the house and saving them from the Luftawee air raid. The British government had imposed a total blackout, without the power cut strategy. They wanted every resident of Britain to paint their windows black, so that not a single ray of light could escape their house.