Long overshadowed by the American Civil War, the Mexican-American War (1846–1848) has received significantly less attention from historians partly because of its questionable origin and controversial outcome. Rather than treat the conflict with a form of historical amnesia, the contributors to this volume argue that the Mexican-American War was a formative experience for the more than three hundred future Civil War generals who served in it as lower-grade officers. The Mexican War was the first combat experience for many of them, a laboratory that equipped a generation of young officers with practical lessons in strategy, tactics, logistics, and interpersonal relationships that they would use later to command forces during the Civil War.