Why did Lincoln not end slavery in the entire United states?

Lincoln's primary goal during the Civil War was to preserve the Union rather than to abolish slavery completely. The Emancipation Proclamation, issued in 1863, freed enslaved people only in the Confederate states, as it was a strategic war measure aimed at weakening the South. Furthermore, he faced significant political opposition, and many in the border states were resistant to the idea of ending slavery entirely. It wasn't until the passage of the 13th Amendment in 1865 that slavery was formally abolished throughout the entire United States.