An often neglected topic of Civil War literature is the role preserving the Union played in motivating the North. Even when the importance of preservation of the Union is acknowledged, it's often relegated to second tier status in favor of emancipation.
University of Virginia professor Gary Gallagher's latest work replaces preservation of the Union as the primary goal for which the North fought, helping 21st century Americans understand why it was so beloved by those willing to die for it. He differentiates this Northern GOAL from the war's CAUSE, which was "beyond dispute...controversies related to slavery." The Union War provides insight into subjective Union views on topics related to the war's aims, although it does not offer an objective assessment of their accuracy (e.g., whether the Union really afford its citizens, particularly those in urban slums and factories the economic opportunities often claimed). At the same time, it disputes the thesis that emancipation emerged as a goal equal to or greater than Union by the war's conclusion. To the vast majority of the North, emancipation remained a necessary tool to prosecute the war, and restoring the status quo ante was unthinkable given how slavery had nearly destroyed their beloved Union.
In a day when we debate concepts such as "American exceptionalism" there was little doubt that it was exceptional in 1861 in terms of popular government, or self-rule by the common (white) man. As flawed as American republicanism was in the middle of the 19th century, it still stood out as the most progressive form of government (if practiced imperfectly), especially when compared to the aristocratic and even more repressive forms of government found in Europe, which had fought, successfully, against republican inspired uprisings only a few years earlier. Fighting for the Union meant, in their view, fighting for the survival of self government and the rule of law in the world (recall Lincoln's "last best hope" rhetoric). To Union soldiers it also meant preserving the legacy of the founding generation, and protecting the inheritance of future generations of Americans.
Gallagher reviews recent scholarship on the Civil War that denigrates the concept of Union as a worthy war aim, explaining why the Union was so important to Northerners. Another interesting theme is Union soldiers' hatred of slaveholders and oligarchs who threatened "liberty," but primarily the Union soldiers' own through their non-free labor economy. He discusses the link that Northerners placed between the Union and economic liberty, something Lincoln and others continually stressed, although, again, he does not evaluate its accuracy (he does, interestingly, cite Karl Marx for the view that Union victory would preserve the most progressive form of government heretofore existent and provide many oppressed Europeans with the potential for a small degree of economic autonomy in the form of western lands).
Overall, Gallagher's work is a "most read" for students of American history. It stands as a reminder that ideas have consequences, and provides us with exactly what good history does: a window into a time period as seen through the eyes of those who lived it, rather than through the distorting lens of time that has led some to condescending, ahistorical conclusions about those who fought and died to preserve the Union.