What was important about the Antietam battle?

It was the bloodiest day of the Civil War and because Lee withdrew to
Virginia the Union was considered the victor. Both France and England
had contemplated siding with the Confederates until this battle. After
the battle both nations withheld recognition of the South.
2,108 Union troops were killed and 9,549 were wounded. The South
lost about 2,700 killed and 9,029 wounded. Two things followed the battle on 17 September 1862 which may have
had long term significance to the outcome of the Civil War. President
Lincoln was able to release the Emancipation Proclamation and England
and France failed to side with the Confederate States.