And after that, President Lincoln added yet another slave state to the most powerful slave nation in North America - the United States.
Brings to mind the observation of the London Spectator: “The Government liberates the enemy’s slaves as it would the enemy’s cattle, simply to weaken them in the coming conflict . . . the principle asserted is not that a human being cannot justly own another, but that he cannot own him unless he is loyal to the United States.”
Be that as it may. Just answering your question. Motivation has little to do with the act. The Union Army freed 3 million slaves.