Hi Mike, you helped me out one other time here is another question.
To what extent were Lincoln's war aims altered by the Emancipation Proclamation? and Why did he specify that the proclamation was
"a fit and necessary war measure"?
At the outset of the War, Lincoln went to great lengths to make clear that he did not intend to end slavery in the South, nor did he believe he had the Constitutional right to do so. Four States where slavery was legal remained in the Union. Many other northerners did not have a problem with slavery and had no desire to fight in a war to end slavery. Therefore, to keep these people in the Union cause, Lincoln focused on the need to save the Union rather than ending slavery, as the cause of the war.
But of course slavery was the great issue that divided the country and fear of ending slavery was a major reason why the southern States had seceded. Despite his protestations that he would not try to end or even limit slavery in the States where it already existed, it was well known that Lincoln was an opponent of slavery and hoped that it would eventually come to an end. So Lincoln had a delicate balance of keeping pro-slave northerners on his side to save the Union, while also dealing with the growing abolitionist movement that wanted to make the war about ending slavery.
The Emancipation Proclamation tried to walk that balance by ending slavery only as a war measure and only in the States that were in rebellion. Northern States where slavery was still legal were not affected by the Proclamation. Lincoln portrayed the proclamation as a war measure to hurt the south, the same as confiscating or destroying other property in pursuit of winning the war. It was also done in order to keep Britain from allying with the South. Britain had a strong cotton trade with the South and would be eager to build better relations with the Southern States if they became independent. But England had also outlawed slavery several decades earlier and had a strong abolitionist movement. The Proclamation helped make clear that the war was more about slavery, which was seen as a way of keeping Britain from deciding to help the South.
Lincoln's immediate war aims did not change as a result of the Proclamation. But over the next few years, it became clearer that the war would decide the slavery question entirely. By the end of the war, it seemed much more likely that a Union victory would mean the end of slavery. That is, in fact, what happened with the passage of the 13th Amendment. The Proclamation was the first step in pushing the North to make that connection between victory and abolition.
I hope this helps!