When the Cold War ended, the global alignment between supporters of the United States, supporters of the Soviet Union, and countries that tried to remain unaligned yielded to new regional relationships in which many middle powers exerted increased influence. Increasingly assertive middle powers, countries with significant economic influence either in relation to their neighbors or in broader trade networks, jockeyed for regional leadership, sometimes bringing them into conflict. Brazil, a rapidly industrializing country with 200 million people and vast territory and resources, emerged as the dominant nation-state in South America. Mexico, both highly industrialized and economically integrated with the United States, emerged as the leader of the Spanish-speaking Americas. France and Germany re-emerged as central economic powers in Europe. Nigeria and South Africa became the leading powers in sub-Saharan Africa. Turkey, Egypt, and Israel were also regional powers in the Middle East. Iran and Iraq fought for dominance in the Persian Gulf. China, India, and Japan all became leading regional powers, and several other Asian countries — notably South Korea, Indonesia, and Pakistan — were determined to join them.

While the end of the Cold War reduced superpower pressures that intensified regional conflicts, other factors continued to feed conflicts around the world. In the 1990s civil wars in Bosnia, Kosovo, Rwanda, and Afghanistan killed over a million people and sent hundreds of thousands of refugees running for their lives. Since 2000 new and continuing wars have caused millions more deaths and new refugees, particularly in Syria, Sierra Leone, Liberia, the Democratic Republic of the Congo, Mali, Uganda, Afghanistan, Burundi, Somalia, Iraq, Sudan, and Angola. Rivalries between ethnic groups often lie at the heart of the civil wars that produce so many deaths and refugees. Ethnic competition can lead to demands for ethnic autonomy or political independence.