When The Emancipation Proclamation was issued the nation was in a bloody civil war that had been going on for three years. The Union Military was tasked with uniting a shattered country and it had to invade and conquer an area larger than western Europe. The Union was seen as invaders imposing their will as appose to the Confederates who were being compared to earlier revolutionaries that were motivated fighters defending their homes and families. Although the Union soldiers outnumber the Confederate soldiers, the Confederacy only had to wait out and cripple the Northern support of the war.
The Union lack of military success, the change of northern public opinion, the added strength and resupply of men the freed slaves would provide were