Answer: here:
Although the Battle of Antietam resulted in a draw, the Union army was able to drive the Confederates out of Maryland – enough of a “victory,” that Lincoln felt comfortable issuing the Emancipation just five days later.The Emancipation Proclamation confirmed their insistence that the war for the Union must become a war for freedom. It added moral force to the Union cause and strengthened the Union both militarily and politically.
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