Answer:
The Battle of Antietam was the one of the Bloodiest one day battles of the war at that point that resulted in a decisive win for the Union. This big win gave the Union the knowledge that they could win aganist the confederacy which resulted in a gain of confidence for the Union. This win was a win in more ways than one, it was a win in the Eastern war front which had been a strong hold for the confederacy. Lincoln used the confidence of this win to issue the Emancipation Proclamation from a position of strength rather than need.
Step-by-step explanation: