Gallagher also criticizes recent studies of soldiers' letters and diaries, which find that an antislavery purpose emerged early in the war. These works, he argues, remain highly "impressionistic," allowing the historian "to marshal support for virtually any argument." Whereupon Gallagher embarks on his own equally impressionistic survey of these letters, finding that they emphasize devotion to the Union.
Ultimately, Gallagher's sharp dichotomy between the goals of Union and emancipation seems excessively schematic. It begs the question of what kind of Union the war was being fought to preserve. The evolution of Lincoln's own outlook illustrates the problem. On the one hand, as Gallagher notes, Lincoln always insisted that he devised his policies regarding slavery in order to win the war and preserve national unity. Yet years before the Civil War, Lincoln had argued that slavery fatally undermined the nation's ability to exemplify the superiority of free institutions. The Union to be saved, he said, must be "worthy of the saving." During the secession crisis, Lincoln could have preserved the Union by yielding to Southern demands. He adamantly refused to compromise on the crucial political issue -- whether slavery should be allowed to expand into Western territories.
Gallagher maintains that only failure on the battlefield, notably Gen. George B. McClellan's inability to capture Richmond, the Confederate capital, in the spring of 1862, forced the administration to act against slavery. Yet the previous fall, before significant military encounters had taken place, Lincoln had already announced a plan for gradual emancipation. This hardly suggests that military necessity alone placed the slavery question on the national agenda. Early in the conflict, many Northerners, Lincoln included, realized that there was little point in fighting to restore a status quo that had produced war in the first place.
I'm hoping we might get to this, at some point, if only as a counter-point to Manning's work. But Foner's thoughts mirror some of my own, having heard Gallagher speak a few times about his theory on "Why Union soldiers fought." "Schematic" is a good word for how Gallagher's thesis struck me, but also at once singular and abstract.
Even reading Manning's book, I'm not really convinced that you can arrive at a sole answer for why Union soldiers fought. Which is not to say that an impressionistic take, in Gallagher or Manning's case, is worthless. What I'm getting is some sense of the various arguments circulating in the Army throughout the War. That, in and of itself, has value, even if it isn't the value which the author's claim to offer.
As a side-note, I've started Foner's The Fiery Trial via audiobook. I'm trying to be Civilization on "King," and I think by the time I do that, I'll have finished. So far, I'm really enjoying it. The more I read about Lincoln the more impressed I become. And not impressed like "Oh, he really wasn't racist," but impressed with the quality of his mind, his writing, his ambition. I become impressed with him as a human.