The overall purpose of continuing the civil war to address the issue of slavery rested on a document written by president lincoln called the

The answer is  The Emancipation Proclamation. It was issued by President Abraham Lincoln on January 1, 1863, as the country entered the third year of the Civil War. He declared that "all persons held as slaves … shall be then, thenceforward, and forever free"—but it applied only to states designated as being in rebellion, not to the slave-holding border states of Delaware, Kentucky, Maryland, and Missouri or to areas of the Confederacy that had already come under Union control.

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