Cold War takes spying to new heights

The Cold War refers to the period following World War II when the United States and its allies were enemies with the Soviet Union, now known as Russia, and its allies.

It was 'cold' because unlike a 'hot' war there was no direct fighting between the two countries. Instead, they 'fought' using propaganda, threats and economic pressure.

During the Cold War, the US and the Soviet Union spied on each other using satellites which provided useful data about the other country's infrastructure and activities. Many countries spy on each other - and not just on their enemies - to gain information they think is useful or important.

Cold War hostilities came to an end with the disintegration of the Soviet Union in 1991.