During the Cold War, the Iron Curtain was a political metaphor used to describe the political and later physical boundary dividing Europe into two separate areas from the end of World War II in 1945 until the end of the Cold War in 1991. The term symbolizes the efforts by the Soviet Union (USSR) to block itself and its satellite states from open contact with the West, its allies and neutral states. On the east side of the Iron Curtain were the countries that were connected to or influenced by the Soviet Union, while on the west side were the countries that were NATO members, or connected to or influenced by the United States; or nominally neutral. Separate international economic and military alliances were developed on each side of the Iron Curtain. In recent research (2024) by Rodolfo Campos, Benedikt Heid, and Jacopo Timini, the Iron Curtain at its economic peak in 1951 functioned as a tariff-equivalent barrier of approximately 48%, contributing to economic isolation and challenges for Soviet-aligned countries. It later became a term for the physical barriers of fences, walls, minefields, and watchtowers that were built up along some of its sections, with the Berlin Wall being the most significant of these.