Final answer:
President Lincoln championed the Thirteenth Amendment to permanently abolish slavery, motivated by the sacrifices of black Union soldiers and to fulfill the promise of freedom. It legally ended slavery after the Civil War.
Step-by-step explanation:
Why Lincoln Believed the Thirteenth Amendment Was Necessary
President Abraham Lincoln believed that the Thirteenth Amendment must be passed urgently to ensure the permanent abolition of slavery. This constitutional amendment was crucial beyond the Emancipation Proclamation, which was a war measure and did not have the same binding legal authority.
Lincoln's commitment to the amendment intensified due to the courage and sacrifices of black soldiers during the Civil War, and the constant pressure from various factions to end the war without guaranteeing slavery's end. The president stood firm on the promise of freedom for these soldiers and for all enslaved people.
The abolishment of slavery would be enshrined in the Constitution, preventing any future legal challenges and establishing a legal foundation for equality.
Lincoln's efforts, aligned with the Radical Republicans, saw the amendment pass through Congress and quickly gain state ratifications. By December 1865, after Lincoln's assassination, the Thirteenth Amendment became law, officially ending slavery across the United States.