The Cold War was an elongated state of political conflict, economic competition, and military tension after the World War II principally between the Soviet Union and the United States of America.
The Cold War wasn’t a typical war: there were no enemy planes bombing countries, no tanks or heavy artillery, no troops plundering native habitants and destroying cities and villages. It was a war of interests and ideologies.
The conflict between Eastern and Western parts of the world had deep roots. At the very beginning of the XXth century relations between the USA and Russia could be described as hostile. In the early 1920s, soon after the Communist revolution in Russia, the United States of America provided a famine relief to the Soviet people and little by little contacts between these two countries improved; but by the 1930s the relationship had soured again and after the World War II it had lead to the Cold War.
This unusual war made almost the entire world divide into two hostile camps around two dominant powers fighting to become the dominant power (this phenomenon was called a bipolar system). The United States were trying to spread their democratic ideology to the whole world, whereas the USSR was trying to promote their communist ideology.
I believe that the blame for this war for supremacy can hardly be placed on one country. In some way this war was inevitable due to tremendous differences in the two ideologies.
The Cold War lasted for forty three years and ended in 1991 after the Soviet Union collapse, leaving the USA the dominant power. This also has lead to the establishment of noncommunist political parties and the development of a new democratic state in the former USSR.