The emancipation proclamation was announced after the battle explain as well

a)
shiloh.

b)
vicksburg.

c)
gettysburg.

d)
antietam/sharpsburg.

The answer is D) Antietam/Sharpsburg.

Why is it D)? well its D) because the Confederates had to prove they could win a battle on Union soil (to get Britain and France to join on their side) and the Union had to prove it could stop such an invasion. Antietam/Sharpsburg, a Confederate loss on Union soil, was just such an event.