Later chapters reflect on the nature of slaves' emancipation and the role of Abraham Lincoln in it. One line of argument holds that by "coming into Union military lines in the South, [slaves] forced the issue of emancipation on the administration." Although McPherson gives much credit to their agency, he also points out that the primary mechanism of liberation for most slaves remained the 13th Amendment. Lincoln no doubt deserves credit, then, even if his stance on slavery had not always been as enlightened as it was by war's end. His antislavery convictions actually began as "gradualist and colonizationist" (the latter referring to a plan to help freed slaves emigrate out of the U.S.) and only evolved slowly over the course of the war.
In reestablishing the military context of the war's most important social measure, McPherson argues that the Emancipation Proclamation began as a military strategy to weaken the Confederacy and only later became a national policy. "To win a war over an enemy fighting for and sustained by slavery," he states, it was necessary for the North to "strike at slavery."