Editor’s Note: This column was coauthored by Bob Morrison.

President Abraham Lincoln had been warned by Gen. George B. McClellan not to interfere with the institution of slavery. McClellan was a “War Democrat,” willing to fight to preserve the Union, but unwilling to do anything about the root cause of the rebellion that threatened the life of the nation.

Ironically, it was McClellan’s victory at the Battle of Antietam on September 17, 1862, that had given Lincoln the opportunity he needed to issue his Preliminary Emancipation Proclamation. In that document, the President warned rebellious states in the South that they would have their slaves freed if they did not cease their insurrection against the federal government and once again obey the laws of the Union.

That hundred-day period had been a difficult one for President Lincoln. There would be political reverses in the mid-term congressional elections that fall. Democrats campaigned on the slogan “The Union as it was and the Constitution as it is.” That meant slavery would be secure in all the states where it then existed. They picked up congressional seats and won key state governorships.

And then, there was the disastrous Union defeat at Fredericksburg, Virginia. Thousands of Union soldiers died in thirteen fruitless charges against Marye’s Heights. An extraordinary appearance of the Northern Lights on the night of that battle led people to say the very heavens were draped in mourning.

Now, on January 1, 1863, Lincoln proved true to his word on Emancipation. But, as he sat down to sign the engrossed copy of the historic document, he noted an error in the text. Lincoln knew that the U.S. Supreme Court was hostile to Emancipation. If there was a single error, Lincoln knew the pro-slavery Chief Justice Roger B. Taney would strike down the Emancipation Proclamation. So he ordered it re-copied for signature later that same day.

Meanwhile, President Lincoln had to stand for hours shaking thousands of hands in the traditional New Year’s Day reception at the White House. When he came back to sign the Emancipation Proclamation, his hand was shaking. As his puzzled colleagues looked on, he exercised his weary arm.

He explained: “If I am remembered for anything, it will be for this act and my whole soul is in it.” He did not want future generations to see a feeble signature and say he hesitated. So he signed it “Abraham Lincoln.” He wrote out his full name, not signing it as he usually did, “A. Lincoln.”

January 1, 2013,  the National Archives places the Emancipation Proclamation on rare public display, the text is hardly legible, the victim of age and light. But Abraham Lincoln stands out clearly.

Some cynics today say Lincoln freed no slaves where he had power and all the slaves where he did not. Then, too, the London newspapers adopted a snarky tone: “The high principle of Mr. Lincoln’s proclamation is that a man may not own a man unless he is loyal to Mr. Lincoln’s government.”

That criticism was as ignorant as it was unfair. Lincoln was no despot. He knew that he could not constitutionally deprive loyal citizens of their slaves so long as they obeyed the laws. He pleaded and cajoled the congressmen from the loyal slave states of Missouri, Kentucky, Maryland, and Delaware. They stubbornly refused his offers of compensated emancipation.

Lincoln was an able lawyer who new his brief. He had been a reader of Richmond newspapers for years. When secessionist editors boasted that the South could outlast the North because they could send all their young men into the army, while slaves would work the farms and factories, Lincoln took note.

Because the rebels themselves claimed slavery was a military asset, Lincoln knew he was on solid ground in freeing those slaves. His Emancipation Proclamation was a constitutional exercise of his powers as commander-in-chief of the army and navy. He justified it as an act of military necessity.

Abraham Lincoln is remembered as the Great Emancipator. He knew that the advance of the Union armies would bring freedom to millions.

Lincoln’s bold black signature had done this. And he would do more. As the movie, Lincoln, so clearly shows, the president was the prime mover behind the Thirteenth Amendment to the Constitution. That measure ended slavery in every state. It’s a shame that the able writers and directors of this new movie did not show Lincoln signing that amendment, too. A president’s signature is not necessary for a constitutional amendment, but Lincoln once again had his whole heart and soul in it.

This is the day, January 1, 1863, one hundred fifty years ago, that changed America forever. From that date onward, Father Abraham’s armies, the armies of the United States, became armies of liberation. Those soldiers, black and white, carried freedom in their haversacks.