Most Unparalleled Last Card Played By a Reckless Gambler
With enlistments dwindling and in dire need of recruits, Lincoln would play a last card as did Lord Dunmore in 1775, and Vice-Admiral Alexander Cochrane in 1814.  All three intended to bring the Americans to their knees in the face of slave revolt and race war with an emancipation decree.  Despite Lincoln’s proclamation, only 180,000 of a 3.5 million African population served in the Northern army – perhaps half of them conscripts. These slaves pressed into blue uniforms would be used to build fortifications, cook food, and aid on picket, and in segregated units with white officers.
Bernhard Thuersam, Chairman
North Carolina War Between the States Sesquicentennial Commission
"The Official Website of the North Carolina WBTS Sesquicentennial"

Most Unparalleled Last Card Ever Issued By a Reckless Gambler:
“[On] May 9 [1862], General David Hunter, by an order, proclaimed the slaves free in his department of Georgia, Florida and South Carolina.  May 19, the President [Lincoln] nullified this action….proclaiming that the freeing of slaves would be his responsibility as Commander-in-Chief……
The warm and impulsive [Massachusetts Governor John] Andrew answered a call for troops, May 19, “I think they (our people) will feel the draft is heavy on their patriotism. But if the President will sustain General Hunter, recognize all men, even black men, as legally capable of that loyalty the blacks are waiting to manifest, the roads will swarm, if need be, with multitudes whom New England would pour out to obey your call.”
In July, Hill, the correspondent of the “Tribune,” notes a disheartening conversation with General Wadsworth, who had been in close converse with the President at the War Department many hours, every day, for several months. He regarded Lincoln as wholly “without anti-slavery instincts,” and talking frequently of the “nigger question,” on the wrong side.
September 23 the Proclamation of emancipation – an experiment in government by decree, rare for us, but common in continental Europe – was issued, to become the law of the land January 1, 1863. Ignored hitherto as a political factor in this absorbing drama, whether at Montgomery or Washington, the negro had become a military force of the first importance.
Experts agreed that these poor waifs, an errant factor in civilization, must be taken now from the ciphers dormant before the decimal, and be put into the working columns of figures which represented men. “The labor of the colored man supports the rebel soldier, enables him to leave his plantation to meet our armies, builds his fortifications, cooks his food, and sometimes aids him on picket by rare skill with the rifle,” said General [Montgomery] Meigs on November 18.  “By striking down this system of compulsory labor, which enables the leaders of the rebellion to control the resources of the people, the rebellion would die of itself.”
The immediate results were very disheartening to the President. “The North responds to the proclamation sufficiently in breath; but breath alone kills no rebels.” The radical Republicans welcomed it, but their constituents did not send out in recruits that strong adult element, the lusty thews and sinews from which the working military strength of a nation must be drawn. But in a military sense the radicals embodied the nervous force of the North, rather than the brawny muscle which should subdue the solid enforced strength of the Southern people.
The overwhelming unfriendly majority [of the North] spoke through the “Times.” “The death of slavery must follow upon the success of the Confederates in this war.” But Mr. Lincoln’s emancipation “can only be effected by massacre and utter destruction.” Another sapient critic call the proclamation “the most unparalleled last card ever issued by a reckless gambler.”
(War Government, Federal and State, in Massachusetts, New York, Pennsylvania and Indiana, 1861-1865, William B. Weeden, Houghton, Mifflin and Company, 1906,pp. 117-118, 120-122)