In the first chapter of the book, McPherson relates how he came to write it. While visiting Civil War battlefields where enormous carnage took place, he can’t find a satisfactory answer as to why so many soldiers gave their lives to such a cause, so he sets about trying to find out:

What prompted them to give up several of the best years of their lives—indeed, to give up life itself in this war that killed almost as many American soldiers as all the rest of the wars this country has fought combined? What enabled them to overcome that most basic of human instincts—self-preservation? (5).

Through letters and diaries and historical research, McPherson tells the reader that he is trying to understand the motivations of soldiers—why they fought, why they reenlisted, how they kept going—and he marvels at such determination in the face of so much death.

McPherson also mentions those who snuck away during battle, or found some way to avoid fighting: “Some soldiers admitted to seeking a bombproof position or to skulking” (7). He looks into the motivations of soldiers and delves into their social class to see if he can find some reason for their behavior in battle.