KEY IDEA: SOCIAL AND CULTURAL GROWTH AND CONFLICT: During the postclassical era, the growth of transregional empires and the use of trade networks influenced religions and spread disease. These cross-cultural interactions also led to conflict and affected demographic development.

​KEY IDEA: UNRESOLVED GLOBAL CONFLICT (1945–1991: THE COLD WAR): The second half of the 20th century was shaped by the Cold War, a legacy of World War II. The United States and the Soviet Union emerged as global superpowers engaged in ideological, political, economic, and military competition.

KEY IDEA: HUMAN RIGHTS VIOLATIONS: Since the Holocaust, human rights violations have generated worldwide attention and concern. The United Nations Universal Declaration of Human Rights has provided a set of principles to guide efforts to protect threatened groups and has served as a lens through which historical occurrences of oppression can be evaluated.