The Emancipation Proclamation occurred, without any military assistance.
Debatable...
On July 22, Lincoln met with the members of his Cabinet and shared his idea with them. He presented a preliminary draft of the
Emancipation Proclamation on two pages of lined paper. It would free the slaves in the Confederate states as a “military necessity” by weakening the enemy under his constitutional presidential war powers.
The cabinet agreed with his reasoning even if some members were lukewarm. Some feared the effects on the upcoming congressional elections and that it would cause European states to recognize the Confederacy to protect their sources of cotton.
Secretary of State William H. Seward counseled the president to issue the proclamation from a position of strength after a military victory.
The early victories of the year in the West by Grant at the Battle of Shiloh and the capture of New Orleans were dimmed by a more recent defeat in the eastern theater. Union General George McClellan’s Peninsular Campaign driving toward Richmond was thwarted by his defeat in the Seven Days’ Battles. Nor did Lincoln get the victory he needed the following month when Union armies under General John Pope were routed at the Second Battle of Bull Run.
In September, General Robert E. Lee invaded the North to defeat the Union army on northern soil and win European diplomatic recognition. He swept up into Maryland. Even though two Union troops discovered Lee’s plan of attack wrapped around a couple of cigars on the ground, McClellan did not capitalize on his advantage. The two armies converged at Sharpsburg near Antietam Creek.
At dawn on September 17, Union forces under General Joseph Hooker on the Union right attacked Confederates on the left side of their lines under Stonewall Jackson. The opposing armies clashed at West Woods, Dunker Church, and a cornfield. The attack faltered, and thousands were left dead and wounded.
Even that fighting could not compare to the carnage in the middle of the lines that occurred later in the morning. Union forces attacked several times and were repulsed. The battle shifted to a sunken road with horrific close-in fighting. Thousands more men became casualties at this “Bloody Lane.”
The final major stage of the day’s battle occurred further down the line when Union General Ambrose Burnside finally attacked. The Confederate forces here held a stone bridge across Antietam Creek that Burnside decided to cross rather than have his men ford the creek. The Confederates held a strong defensible position that pushed back several Union assaults. After the bridge was finally taken at great cost, the advancing tide of Union soldiers was definitively stopped by recently-arrived Confederate General A.P. Hill.
The battle resulted in the grim casualty figures of 12,400 for the Union armies and 10,300 for the Confederate armies. The losses were much heavier proportionately for the much smaller Confederate army. General McClellan failed to pursue the bloodied Lee the following day and thereby allowed him to escape and slip back down into the South. While Lincoln was furious with his general, h
e had the victory he needed to release the Emancipation Proclamation.
On September 22, Lincoln issued the preliminary Emancipation Proclamation. It read that as of January 1, 1863, “All persons held as slaves within any state, or designated part of a state, the people whereof shall then be in rebellion against the United States shall be then, thenceforward, and forever free.” If the states ended their rebellion, then the proclamation would have no force there.
constitutingamerica.org
Side note: Army of Virginia could have been destroyed after Antietam....but McClellan was overly cautious as per usual...might have ended he war in 1863.