Abolitionists had long been urging Lincoln to free all slaves. In the summer of 1862, Republican editor Horace Greeley of the highly influential New York Tribune wrote a famous editorial entitled “The Prayer of Twenty Millions” demanding a more aggressive attack on the Confederacy and faster emancipation of the slaves: “On the face of this wide earth, Mr. President, there is not one … intelligent champion of the Union cause who does not feel … that the rebellion, if crushed tomorrow, would be renewed if slavery were left in full vigor … and that every hour of deference to slavery is an hour of added and deepened peril to the Union.”
Lincoln responded in his Letter To Horace Greeley from August 22, 1862, in terms of the limits imposed by his duty as president to save the Union:
If there be those who would not save the Union, unless they could at the same time save slavery, I do not agree with them. If there be those who would not save the Union unless they could at the same time destroy slavery, I do not agree with them. My paramount object in this struggle is to save the Union, and is not either to save or to destroy slavery. If I could save the Union without freeing any slave I would do it, and if I could save it by freeing all the slaves I would do it; and if I could save it by freeing some and leaving others alone I would also do that. What I do about slavery, and the colored race, I do because I believe it helps to save the Union; and what I forbear, I forbear because I do not believe it would help to save the Union…. I have here stated my purpose according to my view of official duty; and I intend no modification of my oft-expressed personal wish that all men everywhere could be free”
Lincoln scholar Harold Holzer wrote in this context about Lincoln’s letter: “Unknown to Greeley, Lincoln composed this after he had already drafted a preliminary Emancipation Proclamation, which he had determined to issue after the next Union military victory. Therefore, this letter, was in truth, an attempt to position the impending announcement in terms of saving the Union, not freeing slaves as a humanitarian gesture.