Book excerpt: During the Civil War, the regiment was the fundamental component of armies both North and South, its reliability and effectiveness crucial to military success. Soldiers' devotion to their regiment -- their esprit de corps -- encouraged unit cohesion and motivated the individual soldier to march into battle and endure the hardships of military life. In Brothers One and All, Mark H. Dunkelman identifies the characteristics of Civil War esprit de corps and charts its development from recruitment and combat to the end of the war and beyond through the experiences of a single regiment, the 154th New York Volunteer Infantry. Dunkelman offers a unique psychological portrait of a front-line unit that fought with distinction at Chancellorsville, Gettysburg, Lookout Valley, Rocky Face Ridge, and other engagements. He traces the evolution of natural camaraderie among friends and neighbors into a more profound sense of pride, enthusiasm, and loyalty forged as much in the shared unpleasantness of day-to-day army life as in the terrifying ordeal of battle.