Lincoln's Abolitionist General tells the life story of a general who operated on the vanguard of the advance toward emancipation and the enlistment of African American soldiers. Though not nearly as well known as other senior Union generals, David Hunter participated in signal events of Lincoln's presidency and the Civil War and took advantage of his position to champion the rights of African Americans.

Though Hunter was significantly more radical in his abolitionist sentiments than Lincoln, the two developed a friendship that lasted until Lincoln's death. Miller details the evolution of their relationship, from their early correspondence to Hunter's leading role in the trial of those accused of Lincoln's assassination.

Dealing extensively with Hunter's Civil War experience, Miller recounts the general's wounding at Bull Run and leadership of the Department of the South at Hilton Head Island, where he issued an order to free the slaves and attempted to enlist the first African American Union soldiers.

Crediting Hunter with early advocacy of the "hard war" policies for which William Tecumseh Sherman later became famous, Miller evaluates Hunter's command of the Shenandoah Valley and sheds light both on Hunter's seemingly vindictive treatment of rebel sympathizers and on his puzzling retreat in the Shenandoah campaign of 1864.