Final answer:
When the Civil War began, Lincoln initially fought for the preservation of the Union rather than the abolition of slavery. As the war progressed, he realized that emancipation would weaken the South, increase Union manpower, and pressure Britain to not support the Confederacy. Lincoln ultimately oversaw the passage of the Thirteenth Amendment to abolish slavery.
Step-by-step explanation:
When the Civil War began, President Abraham Lincoln initially stated that the main purpose of the war was to preserve the unity of the United States, rather than the abolition of slavery. While Lincoln detested slavery and believed it should not expand into new territories, he did not initially advocate for immediate abolition or the rights of freed black people in the United States.
However, as the war progressed, Lincoln came to see that ending slavery would provide several advantages for the Union. Firstly, the abolition of slavery would cripple the South's ability to fight, as slaves working in the field freed up southerners to join the Confederate Army. Secondly, embracing emancipation would open the door for the recruitment of African Americans as soldiers, bolstering the Union's manpower. Lastly, it would put pressure on Britain to not recognize the Confederacy since the British public was anti-slavery. Lincoln hoped that proclaiming emancipation would energize citizens in support of the Union cause.
Lincoln's stance evolved throughout the war, and he ultimately oversaw the passage of the Thirteenth Amendment to abolish slavery. However, he did not live to see its ratification.