Why was the Emancipation Proclamation written?

For the civil war slaves had acted to secure their own liberty. So it confirmed their insistence that the war for the Union must become a war for freedom.

From the first days of the Civil War, slaves had acted to secure their own liberty. 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.

explanation:

the addition to geographic boundaries that might have  kept the people of the huang river civilization from traveling to far distance region is that they had learned about the other river valley civilizations but feared contact would bring invasion.

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