The battle of antietam affected the focus of the civil war by
changing it to southern industrialization.
changing it to the construction of a national railroad.
leading to the emancipation proclamation.
leading to the north giving up its antislavery stance.

The Battle of Antietam affected the focus of the Civil War by leading to the Emancipation Proclamation. The correct option among all the options given in the question is the third option. The Battle of Antietam actually pointed out the limitations of both the Union and the Confederate armies. The battle would drag for a long time as it was hard to find a clear winner.