In his actions with respect to emancipation, Lincoln had to proceed according to the dictates of prudence, the virtue that Aristotle claimed was most characteristic of the statesman. Prudence is the practical wisdom that seeks the best means for achieving fixed ends. Thus prudence is concerned with deliberating well about those things that can be other than they are (means). In political affairs, prudence requires the statesman to be able to adapt universal principles to particular circumstances in order to arrive at the means that are best given existing circumstances. For Lincoln to achieve the goal of ending slavery while preserving the Union, he had to choose the means necessary and proper under the circumstances.

In his indispensible book, Lincoln’s Emancipation Proclamation: The End of Slavery in America, Allen Guelzo argues persuasively that Lincoln’s "face was set toward the goal of emancipation from the day he first took the presidential oath." To achieve this goal, he planned to pursue a policy of legislated, gradual, compensated emancipation from the very outset of his presidency. He believed he could convince Congress to appropriate funds to compensate slave owners for gradually freeing their slaves. His plan was to begin where slavery was weakest: in the northernmost slave states, especially Delaware.

The key to his strategy was to convince the legislatures of slave states to change their statutes relating to slavery. The Constitution after all left the issue of slavery to the states. This state legislative strategy also offered the best chance for keeping the issue of emancipation out of the federal court system, where an unfavorable judgment could set back its prospects. This strategy also explains what seems to be his total lack of concern about the consequences of the proposal at the beginning of his term for an amendment foreclosing forever the possibility that the federal government could interfere with the institution of slavery, even by future amendment.

But while he was willing to accept this proposal as a way of bringing the seven states that had seceded back into the Union fold, he adamantly refused any compromise on the expansion of slavery. In a series of letters written to Lyman Trumbull, William Kellogg, Elihu Washburne, and Thurlow Weed in December, 1860, Lincoln adjured them to "entertain no proposition for a compromise in regard to the extension of slavery."

Lincoln believed that if he could prevent the expansion of slavery into the federal territories and prevail upon state legislatures to accept gradual, compensated emancipation (funded by Congress), he could shrink slavery, making it uneconomical and placing it back on the eventual road to extinction that he believed the Founders had envisioned. The outbreak of war derailed the original version of his grand scheme, but even after the war began, Lincoln reasoned that the combination of military success against the Confederacy and compensated emancipation in the loyal slave states would lead to the collapse of the Confederacy, which had staked its hopes on eventually incorporating the so-called border states.

But neither condition came to pass. Lincoln’s proposals for compensated emancipation were rejected by the border-states. Meanwhile, the Confederacy was just now exerting its maximum effort to mobilize its population for war. In April of 1862, the Confederate congress passed a conscription act. Then, abandoning the "cordon" defense that had permitted Union armies to penetrate Confederate territory as far as northern Mississippi in early 1862, the Confederacy organized its mobilized manpower into field armies. One of these forces, the Army of Tennessee struck Grant at Shiloh. Lee’s Army of Northern Virginia drove McClellan back from the gates of Richmond. Then in the fall of 1862, the former invaded Kentucky and the latter invaded Maryland. To a great extent, the South was able to do this only because slave labor freed white men to fight.

Lincoln concluded that he did not have the time to pursue his preferred legislative strategy in the border states and that therefore something stronger and more precipitous was needed to bring the war to a successful conclusion. The Emancipation Proclamation was Lincoln’s response to the failure of Union arms and compensated emancipation. The time had come, as he wrote to Cuthbert Bullitt, to stop waging war "with elder-stalk squirts, charged with rose water." Thus after Lee’s invasion of Maryland was turned back at Antietam, Lincoln issued a preliminary Emancipation Proclamation on 22 September that gave the Confederates one hundred days to submit to the Union or face the prospect of immediate emancipation.

Southern Unionists, loyal slave-holders, and Democrats charged that Lincoln was "revolutionizing" the war by issuing his proclamation. Lincoln did not disagree, admitting that once the proclamation took effect, "the character of the war will be changed. It will be one of subjugation and extermination." But, as he wrote to another correspondent, "This government cannot much longer play a game in which it stakes all, and its enemies stake nothing. Those enemies must understand that they cannot experiment for ten years trying to destroy the government, and if they fail still come back into the Union unhurt" Lincoln took particular exception to the demand by loyal slave-holders "that the government shall not strike its open enemies, lest they be struck by accident." This demand by border state representatives, who had recently rejected Lincoln’s last proposal for compensated emancipation, had become "the paralysis—the dead palsy—of the government in this whole struggle."

Militarily, emancipation was a war measure designed to attack the Southern economy directly. As General-in-Chief Henry Halleck explained to Grant, "The character of the war has very much changed within the last year. There is now no possible hope of reconciliation… We must conquer the rebels or be conquered by them… Every slave withdrawn from the enemy is the equivalent of a white man put hors de combat." But to the extent that slaves came under control of Union forces, they could be substituted for soldiers who were required to labor, freeing them up to fight. Thus emancipation had the effect of transferring labor from South to North, increasing the fighting potential of Union armies while decreasing that of the Confederate armies. As Gideon Welles, Lincoln’s Secretary of the Navy, recalled, the President called emancipation "a military necessity, absolutely essential to the preservation of the Union. We must free the slaves or be ourselves subdued. The slaves were undeniably an element of strength to those who had their service, and we must decide whether that element should be with us or against us"

Militarily, the Emancipation Proclamation opened the way to the next logical step in this process of weakening the South while strengthening the North: enrolling blacks as soldiers in the Union army. The manpower boon to the Union was substantial. Some 180,000 black soldiers served in the Union army. They constituted 120 infantry regiments, 12 regiments of heavy artillery, 10 batteries of light artillery, and seven cavalry regiments. At the end of the war, they constituted 12 percent of the Union’s military manpower.

While the material contribution of African-Americans, both freedmen and former slaves, to Union victory was substantial, their participation in the war to achieve their own liberty was important for its own sake. Without their participation, the war to save the Union "as it was" could not have been transformed into a war to save the Union "as it should be," i.e. without slavery, and it is unlikely that African-Americans could ever have achieved full citizenship and equality in the United States.

Lincoln took an immense gamble by issuing the Emancipation Proclamation. It was foremost a political gamble. Those who argue that Lincoln was only "waiting for the right time" to issue the Proclamation must confront the fact that because of his action, the Republicans paid an enormous price during the 1862 elections. Lincoln put the most highly charged issue of the war before the voters in the midst of an un-won conflict. Votes for Republicans fell by 16 percent from 1860. The Party suffered disastrous setbacks in Pennsylvania, Indiana, Ohio, New York and New Jersey.

Such losses in the elections of 1862 led some to conclude that Lincoln would not issue the final Emancipation. He did so for reasons that he made clear in his annual message to Congress for 1862. "Fellow citizens, we cannot escape history… The fiery trial through which we pass, will light us down, in honor or dishonor, to the latest generation… The dogmas of the quite past, are inadequate to the stormy present… In giving freedom to the slave, we assure freedom to the free… We must disenthrall ourselves, and then we shall save our country."

The Proclamation was also a gamble because it opened the possibility that emancipation would end up in the federal courts. Lincoln feared that if the federal judiciary under Chief Justice Roger Taney ever took up emancipation, it would become in effect the guarantor of slavery, setting back the prospect for all future emancipation just as Dred Scott had set back the effort to prevent the expansion of slavery into the Territories. The fact that the Prize Cases, which essentially affirmed the legality of the Union’s conduct of the war, were decided by a vote of only 5-4 in the midst of the war seems to confirm Lincoln’s desire to keep emancipation out of the courts.

This desire also explains his preference for compensated emancipation over the alternatives: treatment of fugitive slaves under federal control as "contrabands of war;" confiscation; and emancipation as part of martial law. All, he believed, were unconstitutional and open to legal challenge. Indeed, it was possible that even after a successful war to subdue the rebellion, a slave holder whose property had been seized in this manner could sue successfully in federal court. "…[O]nce the war emergency was over," writes Guelzo, "the federal dockets would fill up with appeals that either attacked [martial law emancipation] proclamations as unconstitutional or denied that specific cases really fell within the definitions of the proclamation."

In addition, these alternatives put Lincoln in a quandary concerning the status of the Confederacy. To apply confiscation and contraband as they were understood in international law gave the Confederacy belligerent status. This was at odds with Lincoln’s insistence that the states of the Confederacy could never legally leave the Union. On the other hand, if the war was only a domestic rebellion, as Lincoln held, then confiscation of slave contraband violated the constitutional prohibition against attainder.

A similar problem arose with the use of martial law to effect emancipation. For this reason Lincoln revoked the emancipation that General John C. Fremont proclaimed in Missouri at the beginning of the war. Lincoln believed that to invoke emancipation for political rather than for military reasons—as Fremont had—was unconstitutional. Lincoln argued that no general had such authority.

Additionally, Lincoln believed Fremont’s action would antagonize the loyal slave states, providing them an impetus to join the Confederacy. As he said in a letter to Orville Browning, "I think to lose Kentucky is nearly to the same as to lose the whole game. Kentucky gone, we cannot hold Missouri, nor, as I think, Maryland. These all against us, and the job on our hands is too large for us."

Some have argued that the Emancipation Proclamation actually freed no slaves and that it was the slaves themselves who, by running away, put pressure on Lincoln and Congress to "catch up" with the reality of self-emancipation? Guelzo shows that this argument has things backward. Lincoln may not have had the power on January 1, 1863 to free every slave in the Confederacy, but he had the authority to do so, and in law the authority is as good as the power. And it was the Emancipation Proclamation that provided the impetus for many slaves in territory not under federal control to run away.

Perhaps more significantly, those runaways could not have remained "self-emancipated" for very long without the legal freedom conferred by the Proclamation. As Guelzo has observed, "without the Proclamation, even a Confederacy in defeat would have retained legal title to its slaves, and there is little in the oppressive patterns of coercion Southerners employed before the Civil War or afterward in Reconstruction to suggest that they would not have been willing to reclaim as many of their self-emancipated runaways as they could, and if the record of the federal courts in the post-Civil War decades is any proof, the courts would probably have helped them."

Mackubin T. Owens is an Adjunct Fellow of the Ashbrook Center and an associate dean of academics and professor of national security affairs at the Naval War College.