On August 22, 1862, Lincoln replied to an angry abolitionist who demanded that he attack slavery. “My paramount objective in this struggle is to save the Union,” Lincoln said, “and is not either to save or destroy slavery. If I could save the Union without freeing any slave I would do it, and if I could save it by freeing all the slaves I would do it; and if I could save it by freeing some and leaving others alone I would also do that.” At first glance, Lincoln seemed to restate his old position that union was the North’s sole objective. Instead, Lincoln announced that slavery was no longer untouchable and that he would emancipate every slave if doing so would preserve the Union.

By the summer of 1862, events were tumbling rapidly toward emancipation. On July 17, Congress adopted the second Confiscation Act. The first had confiscated slaves employed by the Confederate military; the second declared all slaves of rebel masters “forever free of their servitude.” In theory, this breathtaking measure freed most Confederate slaves, for slaveholders formed the backbone of the rebellion. Congress had traveled far since the war began.

Lincoln had too. By July, 1862, the president had come to believe that emancipation was “a military necessity, absolutely essential to the preservation of the Union.” The lengthening casualty lists had finally brought him around. In September, he announced his preliminary Emancipation Proclamation that promised to free all the slaves in the seceding states on January 1, 1863. The limitations of the proclamation—it exempted the loyal border states and the Union-occupied areas of the Confederacy—caused some to ridicule the act. The Times (London) observed cynically, “Where he has no power Mr. Lincoln will set the negroes free, where he retains power he will consider them as slaves.” But Lincoln had no power to free slaves in loyal states, and invading Union armies would liberate slaves in the Confederacy as they advanced.

By presenting emancipation as a “military necessity,” Lincoln hoped to disarm his conservative critics. Emancipation would deprive the Confederacy of valuable slave laborers, shorten the war, and thus save lives. Democrats, however, fumed that the “shrieking and howling abolitionist faction” had captured the White House and made it “a nigger war.” Democrats gained thirty-four congressional seats in the November 1862 elections. House Democrats quickly proposed a resolution branding emancipation “a high crime against the Constitution.” The Republicans, who maintained narrow majorities in both houses of Congress, barely beat it back.

As promised, on New Year’s Day 1863, Lincoln issued the final Emancipation Proclamation. In addition to freeing the slaves in the rebel states, the Emancipation Proclamation also committed the federal government to the fullest use of African Americans to defeat the Confederate enemy.