While the Cold War had the effect of creating larger military expenditures in powerful countries and violent conflicts in poor countries, the greatest lasting impact was its effect on the global economy. The most obvious impact of the Cold War was the introduction of global interdependence. Increasingly, countries came to realize that their economic success depended on cooperation with other countries. This was especially true of the first world nations, those countries that Allied themselves with the United States and the West. The roots of globalization can be found in the partnerships that were established shortly after World War II. These partnerships include the European Union (EU), Organization of Petroleum Exporting Countries (OPEC), and North American Free Trade Agreement (NAFTA). Each of these organizations partners with its members to create favorable trade conditions. Additionally, the money that flowed to the countries of Western Europe through the Marshall Plan guaranteed future cooperation between the United States and Western Europe and helped to strengthen those economies for trade.