The president hardly exaggerated when he observed that “the religious people of the country” had extended him “the most unanimous support.” But his invocation of religion was not just the stuff of political design. Just prior to the Union’s costly win at Antietam in September 1862, Lincoln — who had drafted a preliminary Emancipation Proclamation but agreed to hold it until the next Union victory, lest it seem a measure born of desperation — informed his cabinet that he would regard the battle’s outcome as an indication of Divine will on the momentous issue of presidential emancipation. Even the final draft of the Emancipation Proclamation, which was in most respects a dry, legalistic document, included an appeal to God. Lincoln deliberately framed the order as a war measure, not a moral blow against slavery. He needed political cover: Conservative Republicans and War Democrats might accept emancipation as a means to weaken the Confederacy, but not as a war aim. He also needed legal cover: He had no authority to expropriate the property of citizens unless he did so in his capacity as commander in chief, in the service of putting down an armed rebellion. Still, at the urging of his treasury secretary, Salmon P. Chase, he closed: “Upon this act, sincerely believed to be an act of justice, warranted by the Constitution, upon military necessity, I invoke the considerate judgment of mankind, and the gracious favor of Almighty God.”
Lincoln’s wife Mary told William Herndon, Lincoln’s former law partner and later biographer, that for the better part of their marriage, “Mr. Lincoln had no hope & no faith in the usual acceptation of those words; he never joined a Church.” While she felt that Lincoln had always been spiritual in some indeterminate sense, it was only “when Willie died” that he began to turn to religion as a way to make sense of the tragedy that befell his family and the larger tragedy that enveloped the nation he had been chosen to lead. “He felt religious More than Ever about the time he went to Gettysburg,” she remembered, referring to his visit to Pennsylvania in November 1863 to attend the formal dedication of the Union cemetery. Though he was “not a technical Christian [he] read the bible a good deal about 1864.”