"Battle Cry of Freedom" covers two decades, the period from the outbreak of the Mexican–American War to the Civil War's ending at Appomattox. Thus, it examined the Civil War era, not just the war, as it combined the social, military and political events of the period within a single narrative framework. Historian Hugh Brogan, reviewing the book, commends McPherson for initially describing "the republic at midcentury" as "a divided society, certainly, and a violent one, but not one in which so appalling a phenomenon as civil war is likely. So it must have seemed to most Americans at the time. Slowly, slowly the remote possibility became horrible actuality; and Mr. McPherson sees to it that it steals up on his readers in the same way."