Speaking to a fractured country for the first time as president, Abraham Lincoln endorsed a constitutional amendment designed to permanently safeguard slavery in every state in which the institution already existed. If that proslavery provision had been ratified, it would have become the Thirteenth Amendment to the U.S. Constitution. Three years later, Lincoln again threw his support behind a constitutional amendment to address slavery: this time to abolish it. Formally ratified in 1865, this is the Thirteenth Amendment we know today. What happened in those intervening years that led Lincoln to switch from supporting a proslavery amendment to embracing the antislavery provision that ultimately became enshrined in the Constitution? Why did the Thirteenth Amendment of 1864–65 win out over that of 1861? Lincoln himself provided a key to understanding: “I claim not to have controlled events,” he said, “but confess plainly that events have controlled me.” In Emancipation War award-winning journalist Damon Root chronicles the great legal, political, and military struggle to amend the U.S. Constitution to outlaw slavery once and for all. It is the story of canny political tacticians and unyielding radicals; of famous orators and unsung pamphleteers; of liberty-minded Union officers and enslaved persons who liberated themselves by following the North Star to freedom, and who then, in some cases, donned uniforms and took up arms against their former enslavers. It was this wide-ranging movement against slavery—operating both inside and outside the halls of government power, fighting both on and off the battlefield—that made an antislavery constitutional amendment possible. Telling the story from both the top down and the bottom up, Emancipation War provides a gripping and revealing new history of the Thirteenth Amendment.