The Cold War, which happened between the end of the World War II (1945) and the extinction of the Soviet Union (1991), is the name attributed to the historical period of strategic disputes and indirect conflicts between the United States and the Soviet Union, disputing the political, economic and military hegemony in the world.
With the end of World War II, the contrast between capitalism and socialism was predominant between politics, ideology, and military systems. Despite the rivalry and attempt to influence other countries, the United States did not conflict with the Soviet Union (and vice versa) with armaments, as both countries held large amounts of nuclear weapons, and a direct armed conflict would mean the end of the two countries and possibly life on our planet.
With the goal of strengthening capitalism, US President Harry Truman launches the Marshal Plan, which was a low-interest loan offering and investments so that countries devastated in World War II could recover economically. From this strategy the Soviet Union created, in 1949, the Comecon, which was a kind of contestation to the Marshall Plan that prevented its socialist allies from being interested in the favor proposed by the then political enemy.
The lack of democracy, economic backwardness and crisis in the Soviet republics eventually accelerated the crisis of socialism in the late 1980s. In 1989 the Berlin Wall fell and the two Germanies were reunified.
In the early 1990s, then-President of the Soviet Union, Gorbachev, began to accelerate the end of socialism with economic reforms, agreements with the US and political changes.