In villages and towns across Spain and its former New World colonies, local performers stage mock battles between Spanish Christians and Moors or Aztecs that range from brief sword dances to massive street theatre lasting several days. The festival tradition officially celebrates the triumph of Spanish Catholicism over its enemies, yet this does not explain its persistence for more than five hundred years nor its widespread diffusion.

In this insightful book, Max Harris seeks to understand Mexicans' "puzzling and enduring passion" for festivals of moros y cristianos. He...