For a year and a half, Lincoln insisted that the North fought strictly to save the Union and not to abolish slavery. Nevertheless, the war for union became a war for African American freedom. Each month the conflict dragged on, it became clearer that the Confederate war machine depended heavily on slavery. Rebel armies used slaves to build fortifications, haul materiel, tend horses, and perform camp chores. On the southern home front, slaves labored in ironworks and shipyards, and they grew the food that fed both soldiers and civilians. As Frederick Douglass put it, slavery was the “stomach of this rebellion.” Slavery undergirded the Confederacy as certainly as it had the Old South. In the field among Union military commanders, in the halls of Congress, and in the White House, the truth gradually came into focus: To defeat the Confederacy, the North would have to destroy slavery. “I am a slow walker,” Lincoln said, “but I never walk back.” Lincoln’s Emancipation Proclamation began the work, and soon African Americans flooded into the Union army, where they fought against the Confederacy and for black freedom.