In the mid-nineteenth century various groups formed north of the border to invade Mexico. They were called filibusters (from the Dutch "vribuiter," meaning pirate or free booty). The Mexican government saw these invasions as a threat to sovereignty. To Mexico it was significant that the groups recruited, organized, and plotted their "entradas" from the United States in full view of the U.S. government even as newspapers in both countries published dozens of articles about the endeavors.
There were many types of filibusters, from small groups of cutthroats who were satisfied with raiding...

In the decades following the Mexican Revolution, regional strongmen vied with powerful generals and popular rebels for control of Mexico's future. During this era of uprisings, government corruption, and political intrigue, Mexico took its first, faltering steps toward democracy. In the midst of the turmoil, plainclothes agents, traveling under multiple aliases and reporting in code to their superiors, served as "the eyes and ears" of the national government. In "Spies, Politics, and Power: El Departamento Confidencial en Mexico, 1922-1946," Joseph A. Stout traces the development of Mexico's...