The correct answer to this open question is the following.
Although there are no options attached we can say the following.
Lincoln issued this order in 1863 when the war was still going on. Is this a good war strategy?
First, let's clarify the context. Here we are talking about the Emancipation Proclamation issued by the United States President Abraham Lincoln in 1863, in the middle of the Civil War.
Was this a good war strategy?
It was not the best was strategy because the war was not decided yet. Both, Confederates and the Union Army had their chances to win the American Civil War at that moment.
However, Lincoln saw the Emancipation Proclamation of January 1863 as a way to exert some kind of military and moral pressure over the Confederated states, sending the clear message that the President of the Union was confident enough on winning the war and let the Confederates know what would happen when the war was over.
Let's have in mind that the Proclamation was valid to free black slaves in the Confederate states in the South.
Six months later, in July 1863, the Union Army would win the Battle of Gettysburg, one of the bloodiest battles of the Civil War. That victory gave the Union a considerable advantage in the war scenario.