Disunion follows the Civil War as it unfolded.

On Sept. 22, 1862, Abraham Lincoln promulgated the preliminary Emancipation Proclamation, which set the stage to free all slaves in territory controlled by Confederate forces. It changed the nature of the Civil War. But did it, as many say, suddenly turn a war to preserve the Union into a war to create freedom? Answering that question requires an understanding of the Preliminary Proclamation in the context of events that had been developing for many months.

The Proclamation, though symbolically important, was simply the latest in a long string of high-profile emancipatory steps by the federal government. In the summer of 1861 the War Department adopted a policy that allowed for the emancipation of slaves who escaped to Union Army lines, a policy that evolved out of Gen. Benjamin F. Butler’s refusal to return fugitive slaves to their Confederate masters on the theory that they were “contrabands of war.” By September 1862 perhaps 100,000 Southern slaves had gained their freedom in this way. Thus, well before Lincoln issued the preliminary proclamation the United States was providing safe haven for slaves who escaped from the Confederacy.

Moreover, working with Congress, in 1861 and 1862, Lincoln signed the First and Second Confiscation acts, which allowed for the emancipation of slaves owned by rebel masters. The process of freeing slaves under these laws was cumbersome, but the underlying principle was clear: the United States government had the power to free slaves owned by those in rebellion.

Then, in the spring of 1862 Lincoln signed legislation ending slavery in the District of Columbia and the federal territories. For the first time in the history of the United States, the national government had abolished slavery in a jurisdiction.

In May 1862 Maj. Gen. David Hunter, the Union commander in South Carolina, ordered the emancipation of all slaves in that state, as well as Florida and Georgia. Lincoln overruled Hunter’s order because the president correctly understood that he, not a military officer, should make policy. But in overruling Hunter, the president made it clear that if he felt ending slavery was necessary to help preserve the Union, he would act.

Lincoln made other private and public statements outlining the government’s emancipation agenda: he told a group of Congressmen from the loyal slave states that General Hunter’s proclamation had been very popular and that he considered Hunter an “honest man” and “my friend.” In August he published a letter in The New York Tribune, telling Americans he was prepared to free some or all of the slaves in the South in order to save the nation. It was no surprise, then, when Lincoln announced in September 1862 his plans to end slavery in the Confederacy.

The Preliminary Proclamation did not, however, go into effect immediately. Instead Lincoln declared that he would not implement it until Jan. 1, 1863. Some contemporary critics, and some modern historians, criticized Lincoln for not immediately ending slavery, instead of promising to do so 100 days later. To them, it is evidence that Lincoln still had hopes of reuniting the country without ending slavery, as it gave the residents of the Confederacy time to reconsider secession, come back to the Union and retain their slaves.

This criticism is misplaced. Lincoln delayed issuing the final Emancipation Proclamation not as a gesture to the South but as a gesture to conservatives in the North, who might have feared Emancipation. This delay would allow these Northerners to get used to the idea that the end of slavery was coming. Lincoln was essentially telling those in the North who were worried about black freedom that he would give the South one final chance to come to its senses and return to the Union.

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But Lincoln surely knew that this political gesture was not going to stop emancipation. He knew that even if the leaders of the Confederate states changed their minds and wanted to return to the Union, it is unlikely they could have reversed secession in just three months. And that wasn’t going to happen: they were committed to maintaining a nation that was conceived in slavery and dedicated to the proposition that all men were not created equal.

There was another factor preventing the South from laying down its arms. Lincoln had made the crucial decision to use former slaves to defeat the Confederacy. On Aug. 17, more than a month before he would issue the Preliminary Proclamation, Lincoln signed two laws allowing for the enlistment of black troops, the Second Confiscation Act and the Militia Act of 1862. A week later, on Aug. 25, Secretary of War Edwin M. Stanton authorized Gen. Rufus Saxon, who was based at Hilton Head, S.C., to begin to enlist black troops.

Thus, by the time he issued the Preliminary Proclamation, Lincoln had taken the one step that guaranteed the Confederate states would not return to the Union. Southern whites had created a nation based on “slavery subordination,” as Vice President Alexander Stephens declared. The leaders of this slaveholding nation would never voluntarily accept peace with an enemy that was arming former slaves and enlisting them alongside white men.

As he had promised, Lincoln issued the final Emancipation Proclamation on Jan. 1, 1863. In that document, he specifically and unequivocally endorsed the use of black soldiers, stating: “And I further declare and make known, that such persons of suitable condition, will be received into the armed service of the United States to garrison forts, positions, stations, and other places, and to man vessels of all sorts in said service.”

On Sept. 22, 1862 the war to preserve the Union became a war to create freedom. Lincoln was committed to ending slavery in the Confederacy and using black troops – former slaves – to help accomplish this. He was not only committed to enlisting black soldiers, but was in the process of doing so. Once in uniform, once armed, once they had faced their former master in combat, these newly created American soldiers would become an irrefutable argument for ending all slavery in the nation.

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Paul Finkelman is the John Hope Franklin visiting professor of American legal history at Duke Law School and the President William McKinley distinguished professor of law and public policy at Albany Law School.