This innovative study offers the first-ever comparison of the military roles played by commissars, political officers, and chaplains in military settings ranging from the armies of Cromwell, the Jacobins, the Nazis, the Soviets, and the United States. Despite the stark differences in the political systems of the countries of these disparate armed forces, Dale R. Herspring argues that there are certain critical functions that must be fulfilled in every military, regardless of its ideological orientation. Most vital are motivation, morale boosting, and political socialization. In addition, Herspring's comparative historical analysis decisively demonstrates that the roles of commissars, political officers, and chaplains alike have evolved in ways that are crucial yet rarely understood either by policymakers or scholars.

For both the Union and Confederate soldiers, religion was the greatest sustainer of morale in the Civil War, and faith was a refuge in times of need. Guarding and guiding the spiritual well-being of the fighters, the army chaplain was a voice of hope and reason in an otherwise chaotic military existence. The clerics' duties did not end after Sunday prayers; rather, many ministers could be found performing daily regimental duties, and some even found their way onto fields of battle.

Based on extensive in-depth interviews with more than thirty active duty chaplains regarding their successes, failures and conflicts, the book is about the way military chaplains handle religious diversity among the enlisted they serve and within their own corps.

Civil War Chaplains wondered whose side God was on, and if their ministries might be in vain. They saw, on both sides, God's Spirit at work. Was the Spirit divided, was God punishing both North and South for their sins, or was there some other explanation for this seemingly endless war?

How does religion shape the modern battlefield? Ron E. Hassner proposes that religion acts as a force multiplier, both enabling and constraining military operations. This is true not only for religiously radicalized fighters but also for professional soldiers. In the last century, religion has influenced modern militaries in the timing of attacks, the selection of targets for assault, the zeal with which units execute their mission, and the ability of individual soldiers to face the challenge of war. Religious ideas have not provided the reasons why conventional militaries fight, but religious practices have influenced their ability to do so effectively. In Religion on the Battlefield, Hassner focuses on the everyday practice of religion in a military context: the prayers, rituals, fasts, and feasts of the religious practitioners who make up the bulk of the adversaries, bystanders, and observers during armed conflicts. To show that religious practices have influenced battlefield decision making, Hassner draws most of his examples from major wars involving Western militaries. They include British soldiers in the trenches of World War I, U.S. pilots in World War II, and U.S. Marines in Iraq and Afghanistan. Hassner shows that even modern, rational, and bureaucratized military organizations have taken—and must take—religious practice into account in the conduct of war.