Most Republicans had become convinced by 1862 that the war against a slaveholders’ rebellion must become a war against slavery itself, and they put increasing pressure on Lincoln to proclaim an emancipation policy. This would have comported with Lincoln’s personal convictions, but as president he felt compelled to balance these convictions against the danger of alienating half of the Union constituency. By the summer of 1862, however, it was clear that he risked alienating the Republican half of his constituency if he did not act against slavery.
Moreover, the war was going badly for the Union. After a string of military victories in the early months of 1862, Northern armies suffered demoralizing reverses in July and August. The argument that emancipation was a military necessity became increasingly persuasive. It would weaken the Confederacy and correspondingly strengthen the Union by siphoning off part of the Southern labor force and adding this manpower to the Northern side. In July 1862 Congress enacted two laws based on this premise: a second confiscation act that freed slaves of persons who had engaged in rebellion against the United States, and a militia act that empowered the president to use freed slaves in the army in any capacity he saw fit—even as soldiers.
By this time Lincoln had decided on an even more dramatic measure: a proclamation issued as commander in chief freeing all slaves in states waging war against the Union. As he told a member of his cabinet, emancipation had become “a military necessity…. We must free the slaves or be ourselves subdued…. The Administration must set an example, and strike at the heart of the rebellion.” The cabinet agreed, but Secretary of State William H. Seward persuaded Lincoln to withhold the proclamation until a major Union military victory could give it added force. Lincoln used the delay to help prepare conservative opinion for what was coming. In a letter to journalist Horace Greeley, published in the New York Tribune on August 22, 1862, the president reiterated that his “paramount object in the struggle is to save the Union, and is not either to save or destroy slavery.” If he could accomplish this objective by freeing all, some, or none of the slaves, that was what he would do. Lincoln had already decided to free some and was in effect forewarning potential opponents of the Emancipation Proclamation that they must accept it as a necessary measure to save the Union. In a publicized meeting with black residents of Washington, also in 1862, Lincoln urged them to consider emigrating abroad to escape the prejudice they encountered and to help persuade conservatives that the much-feared racial consequences of emancipation might be thereby mitigated.