The Emancipation Proclamation was a firm demonstration of the President’s executive war powers.

The Southern states used slaves to support their armies on the field and to manage the home front so more men could go off to fight. Thousands of black Americans were forced to support the operations of the Confederate army. Black men and women were forced to build fortifications, work as blacksmiths, nurses, boatmen, and laundresses, and work in factories, hospitals, and armories. In 1863, more than 6,000 accompanied the 71,000 soldiers of the Army of Northern Virginia into Pennsylvania. In a display of his political genius, President Lincoln shrewdly justified the Emancipation Proclamation as a “fit and necessary war measure” in order to cripple the Confederacy’s use of slaves in the war effort.

Lincoln also declared that the Emancipation Proclamation would be enforced under his power as Commander-in-Chief and that the freedom of the slaves would be maintained by the “Executive government of the United States.” he stated: "I do order and declare that all persons held as slaves within said designated States, and parts of States, are, and henceforward shall be free... Such persons of suitable condition will be received into the armed service of the United States... And upon this act, sincerely believed to be an act of justice, warranted by the Constitution, upon military necessity, I invoke the considerate judgment of mankind and the gracious favor of Almighty God...."