Final answer:
Lincoln's perspective changed when he embraced emancipation as a war measure and issued the Emancipation Proclamation in August 1862.
Step-by-step explanation:
One moment in Lincoln's life when his perspective changed was when he shifted to embracing emancipation of the slaves as a war measure. Initially, Lincoln and most Republicans opposed allowing free blacks to enlist in the Union army. However, as the war dragged on and the Union cause flagged, Lincoln began to see emancipation as a way to change the character of the war.
In August 1862, Lincoln was prepared to issue the Emancipation Proclamation. Although he was initially hesitant about the idea, Lincoln believed that freeing the southern slaves would bring a speedy end to the war. The Emancipation Proclamation was a significant policy change that symbolized his commitment to ending slavery and preserving the Union.
Lincoln's perspective changed in response to the evolving circumstances of the war and the increasing urgency to preserve the Union while addressing the moral issue of slavery. He recognized that emancipation could help weaken the Confederacy and give a new purpose to the Union's cause.