* His personal beliefs: Lincoln was a vocal opponent of slavery from a young age. He believed that it was morally wrong to own another human being, and he said so on many occasions. In 1854, he wrote, "I have always hated slavery, I think as much as any Abolitionist."
* The political climate: The issue of slavery was becoming increasingly divisive in the United States in the years leading up to the Civil War. Lincoln believed that the only way to resolve this issue was to end slavery once and for all. He said, "I believe this government cannot endure, permanently half slave and half free."
* Military strategy: Lincoln also believed that ending slavery was necessary to win the Civil War. He realized that the Confederate States of America was largely dependent on slavery for its economy and military strength. By abolishing slavery, he hoped to weaken the Confederacy and bring about a Union victory.
Ultimately, Lincoln's support for the ending of slavery was motivated by a combination of personal beliefs, political considerations, and military strategy. His decision to issue the Emancipation Proclamation in 1863 was a major turning point in the Civil War, and it ultimately led to the abolition of slavery in the United States.