Significantly expanding on previous scholarship around "galvanized Yankees," Garrow begins his study with an overview of Civil War prisons as a whole. He outlines unsavory conditions endured by prisoners of war on both sides, including a lack of proper shelter, food, potable water, and medical care. Notably, Garrow argues that the deplorable conditions of these army prisons were not the only motivator that fueled soldiers' decisions to switch sides as the war waned. Garrow investigates service records, pension files, period newspapers, and regimental histories to uncover the complex motivations of Confederate prisoners of war who joined Federal forces. He documents the individual histories of twelve distinct infantry and calvary regiments, contextualizing the wartime climate, struggles, and political leanings of the soldiers grappling with survival and allegiance during the Civil War.

Alongside Garrow's first volume, From Gray to Blue is an insightful addition to existing Civil War scholarship that will engage and inform both history scholars and general readers.