In the transcript of the Emancipation Proclamation, it states that
"And I further declare and make known, that such persons of suitable condition, will be received into the armed service of the United States to garrison forts, positions, stations, and other places, and to man vessels of all sorts in said service."
This quote refers to slaves that Lincoln "freed" in the rebellious states. The passage above shows that one of the main reasons behind Lincoln's desire to sign the Emancipation Proclamation was to gain more soldiers, specifically African-Americans in the South who wanted to fight against the people who oppressed them for so long. This resulted in the development of different all black regimes for the Union army.
