Answer:
The emancipation proclamation gave the Union the Moral high ground for the war, with it Lincoln changed the reason from the war from keeping the union as one and not allowing the Souther states to seceede to it being about freedom for all. This helped to stop Great Britian, and other European nations from siding with the south.
Step-by-step explanation:
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