In this carefully researched and compelling revisionist account, William Marvel provides a comprehensive history of Andersonville Prison and conditions within it. Based on reliable primary sources—including diaries, Union and Confederate government documents, and letters—rather than exaggerated postwar recollections and such well-known but spurious 'diaries' as that of John Ransom, Marvel's analysis exonerates camp commandant Henry Wirz and others from charges that they deliberately exterminated prisoners, a crime for which Wirz was executed after the war.

According to Marvel, virulent disease and severe shortages of vegetables, medical supplies, and other necessities combined to create a crisis beyond Wirz's control. He also argues that the tragedy was aggravated by the Union decision to suspend prisoner exchanges, which meant that many men who might have returned home were instead left to sicken and die in captivity.