In The Calculus of Violence, historian Aaron Sheehan-Dean (Louisiana State Univ.) taps the presidential papers of Abraham Lincoln and Jefferson Davis, diaries of military leaders, National Archives records, and a plethora of relevant secondary sources to argue that, despite the overwhelming loss of life in the US Civil War, casualties could have been worse. He employs the "just war" principle to elucidate the alternation between restraint and excessive killing practiced by both Union and Confederacy.

The book may be seen as comprising three distinct parts. The first (introduction and chap. 1) concerns factors that escalated the violence, including ardent nationalism, Confederate reaction to Union use of black soldiers, and tolerance of guerrilla fighters. Conversely, violence during and after the Civil War was mitigated by citizens' self-policing, the classification of enemy soldiers as POWs rather than criminals, the adherence to regular means of war, and President Abraham Lincoln's plans for tolerant postwar treatment of the seceding states. Sheehan-Dean stresses that both sides applied the rules of war to sanction various behaviors, as justified by the belligerents' respective constitutions.

Part 2 (chaps. 2–7) details how military personnel and civilians defended or practiced various forms of violence during the war. Calculated rhetorical tactics—especially, the adducing of historical examples and religious analogies—were used to gain support. The author also demonstrates how newspapers and pamphlets were utilized to spread stories about enemy abuses.

The Union Army's controversial strategy of confiscation and pacification was intended to reduce rather than augment violence. Nonetheless, both Union and Confederate militaries endorsed harsh methods during their occupation of enemy territory. Southern leaders particularly resented Union forces' use of hostage-taking and banishment against guerrillas.

Conditions inside POW camps were appalling on both sides; many prisoners died not of wounds but disease. An 1862 agreement permitting timely exchange of POWs was rescinded in 1863. Overall, the mortality rate of Union and Confederate prisoners was similar: 15.5 percent and 12.1 percent respectively.

Sheehan-Dean also discusses how military commissions meted out justice in cases of violence committed by citizens. He finds that only half of 416 death sentences handed down by these tribunals were carried out. He likewise maintains that the increase in military commissions and courts-martial throughout the war attests to efforts to curtail uncontrolled or unnecessary violence.

President Lincoln's strategy of freeing blacks in Confederate states and employing black Union forces during the latter part of the war enraged Southern leaders and citizens alike. It led to the murder of captured black soldiers after the First Battle of Saltville (1–3 Oct. 1864) and the destruction of black residents' property. Such atrocities helped to rationalize the brutal but legitimate methods used by Gen. William T. Sherman to hasten the end the conflict.

The third part of the book (chap. 9 and the conclusion) assesses the use of violence from the perspective of organized governments. The author contends that, though both sides fought the war with an eye to restraining unlawful violence, this proved to be easier for the Union than for the Confederacy, whose acceptance of pseudo-scientific justifications for racism and tolerance of guerrilla forces fostered hate crimes. He notes, too, that new technologies made warfare more lethal than in previous conflicts. Thankfully, early experiments with biological weapons were abandoned.

Sheehan-Dean's new study contributes to a rejuvenated concentration area within Civil War scholarship. One recent study has analyzed diaries and letters of Union and Confederate soldiers to identify their attitudes about war.[1] Others have blamed a breakdown in military discipline for needless civilian casualties involving violence;[2] explained how fugitive slave laws fomented unbridled savagery in the antebellum period;[3] and examined Union and Confederate soldiers' mundane daily routines (like marching) and their sentiments toward fighting and punishment.[4]

Among these innovative new works, Sheehan-Dean's is the most comprehensive and balanced study of the prevalence of violence during the Civil War. It achieves in full its intent to "remind us of a dreadful calculation: the occasional necessity of conflict and the costs it necessarily imposes" (358).