John David Smith is a professor of history at the University of North Carolina at Charlotte. His latest book, co-edited with Mark Elliott, is Undaunted Radical: The Selected Writings and Speeches of Albion W. Tourgée (Louisiana State University Press, 2010).

In 1997, in The Confederate War (Harvard University Press), the historian Gary W. Gallagher argued that contemporary scholars erred in ascribing Confederate defeat to questions of race, class, and gender, and especially to discontent on the home front and ambivalence over slavery's morality. Gallagher, one of the nation's pre-eminent Civil War specialists, marveled not at Confederate weakness but rather at how the outmanned and outgunned Southerners sustained nationalism and popular will as long as they did. "The Confederate military," he concluded, "ultimately proved unable to win enough victories at crucial times to carry their nation to independence." Historians' propensity to emphasize internal Southern weakness, he maintained, resulted "from an understandable tendency to work backward from the war's outcome in search of explanations for Confederate failure."

Just as Gallagher judged historians off track regarding Confederate defeat, he now considers them derailed on the question of what mattered most to victorious Northerners—the concept of the Union. Writing recently on a New York Times blog, Gallagher remarks that "as we approach the sesquicentennial of the Civil War, the meaning of Union to mid-19th-century Americans has been almost completely lost. Americans today find it hard to believe that anyone would risk life or fortune for something as abstract as Union. A war to end slavery seems more compelling, the sort of war envisioned in the film Glory."

Mindful of the importance of African-Americans in the military, political, and social history of the Civil War, Gallagher nonetheless insists that "a concentration on emancipation and race sometimes suggests that Union victory had scant meaning apart from them."...

Gallagher develops this argument in his bold, fast-paced, and provocative The Union War, a work that in its revisionist historiographical tone parallels his earlier book. Recently published by Harvard, The Union War offers a searing critique of what Gallagher terms anachronistic scholarship that privileges emancipation and the agency of African-Americans during the war over loyal citizens' commitment to the concept of a perpetual Union. Accusing historians of allowing "modern sensibilities" to skew their "view of how participants of a distant era understood the war," Gallagher finds, not surprisingly, that their scholarship exposes "the many ways in which wartime Northerners fell short of later standards of acceptable thought and behavior."...

Gallagher takes aim at numerous noted historians, including Orville Vernon Burton, Walter A. McDougall, and David Williams, for undervaluing the seriousness and importance of the concept of the Union to the wartime generation, for emphasizing antebellum America's class and racial shortcomings, for overstating Americans' self-interest, and for condemning America for inequality. According to Gallagher, such historians dismiss the notion of American exceptionalism that President Abraham Lincoln described in December 1862, referring to the Union, then mired in a bloody civil war, as "the last, best hope of earth."...