However, Lincoln believed he had no constitutional authority to free the slaves except in those states where it was deemed a military necessity in order to suppress the rebellion, and freeing slaves was still a risky political act given that there were still slave states loyal to the union, and the initial war aims were centered on preserving the union rather than freeing slaves. As such, the proclamation was a military order issued by Lincoln in his capacity as Commander-in-Chief. The Emancipation Proclamation also allowed for the admittance of freed slaves into the (then-segregated) United States military, an unusual opportunity taken by nearly 200,000 black men, many of them former slaves.
Lincoln first discussed the proclamation with his cabinet in July, 1862, but because of the political implications of this act (including the presence of slave states within the Union), he felt that he needed a Union victory in the Civil War before he could issue it. After the battle of Antietam, in which Union troops turned back a Confederate invasion of Maryland, he issued a preliminary proclamation on September 22, 1862. The final proclamation was then issued in January of the following year.
Despite the lack of any immediate effect on the slaves, the proclamation represented a shift in the attitudes of the North towards its war objectives, where merely reuniting the nation would no longer become the sole outcome. It represented the first step toward the ultimate abolition of slavery in the United States.
In the military, the reaction to this proclamation varied widely with some units coming to near mutiny in protest and desertions were reported because of it. On the other hand, other units were inspired with the adoption of a cause that seemed to them to ennoble their efforts such that at least one unit took up the motto, "For Union and Liberty".
Abroad, as Lincoln hoped, the Proclamation turned foreign popular opinion in favour of the Northern States for its new commitment to end slavery. That shift ended any hope of the Confederate States of gaining official recognition, particularly with the United Kingdom.
See also: History of United States of America