The history of humanity is replete with armed and violent conflicts—wars, insurrections, coups, and terrorism. But many authorities consider the twentieth century, marked by two world wars, to be the most violent era ever. Analysts debate whether the world will become increasingly turbulent or more peaceful during the twenty-first century.

However, some of the world’s regions, such as Africa and the Middle East, are more conflict-ridden than others. In their book The Real World Order: Zones of Peace/Zones of Turmoil, authors Max Singer and Aaron Wildavsky separate world regions into two categories: zones of peace and democracy (North America, Western Europe, Japan, Australasia, and parts of South America) and zones of turmoil and development (Africa, Asia, and Central America). The latter category contains 85 percent of the world’s population, the authors note.

Many...