One hundred fifty years ago, in the summer of 1862, the Civil War was raging and President Abraham Lincoln was starting to scribble away at a document, an ultimatum to the rebellious states: Return to the Union, or your slaves will be freed. Emancipation was a \"military necessity,\" the president later confided to his Cabinet. Lincoln called it \"absolutely essential to the preservation of the Union. We must free the slaves,\" Lincoln said, \"or be ourselves subdued.\" \"He knew that emancipation would start the tidal wave of freedom and that it was irreversible once it started,\" says Lincoln scholar Harold Holzer, \"but he also knew that more work would be required.\" Holzer offers a rethinking of the Emancipation Proclamation in his new book, Emancipating Lincoln: The Proclamation in Text, Context, and Memory. It\'s his 42nd book on Lincoln and the Civil War. Though revisionist critics now say the proclamation was weak — \"delayed, insufficient, and insincere\" — Holzer disagrees. He says Lincoln very carefully calibrated the timing and delivery of this act. \"He did things in this run-up that are perplexing, sometimes unattractive, sometimes scary — to prepare the country for what in his mind would be a revolutionary moment,\" Holzer says. Remember: The country was at war. The intractable culture of racism made a pro-freedom policy a perilous idea. Lincoln knew it could bring down his administration and the Union. Holzer says Lincoln had to fear a virulent backlash from conservative Northern Democrats opposed to racial equality. And he risked triggering secession from the border states — the slave-owning states that had not joined the Confederacy: Maryland, Delaware, Missouri, and above all, his birth state, the crucially strategic Kentucky: \"Lincoln worried that he wanted to have God on his side but he must have Kentucky,\" Holzer says. So that was the context in August of 1862 when Lincoln hosted \"a deputation of free Negroes\" — prominent African-Americans — at the White House. His message to them? It was not, \"you shall be free.\" It was: \"It is better for us both ... to be separated.\" \"He blames them for the war,\" Holzer explains. \"[He] says, if it wasn\'t for your presence here — as if it was voluntary in the beginning — this wouldn\'t be happening. Go where the ban is not upon you, he tells them. Go to the Caribbean, go to Africa. Yeah, they\'re cruel words, they\'re harsh words, they\'re unfriendly.\" So how to understand this \"bitter pill of prejudice,\" as Holzer calls it? Well, he says — it\'s telling that President Lincoln had summoned newspaper reporters to that meeting. \"He wanted this message out,\" Holzer explains. \"What\'s important to keep in mind is that he had written the Emancipation Proclamation. It was languishing in a drawer or burning a hole in his pocket. He knew he was going to do this, but he wanted Northern Americans who were dubious about marching toward racial equality to be assured that he was not doing this for the black race. He was doing this for the Union, to reunite the country, to defeat the rebellion, and he had no concern about blacks, their feelings, their resonance. He does have his finger in the wind.\" Lincoln was trying to mold public opinion, to make the proclamation palatable. And, Holzer says, the president was waiting for the right moment: a Union victory on the battlefield — which finally came at Antietam. Within a week of that victory, Lincoln ordered the rebellious states to obey this ultimatum within 100 days: \"Either return to your legal balance with the Union, end this rebellion, or your slaves will be then, henceforward and forever free.\" There was an immediate backlash: Lincoln\'s Republican Party was punished at the polls in the 1862 elections. Then, on Jan. 1, 1863, Lincoln was to issue the final decree at the White House. \"It was New Year\'s Day and by tradition there was a party,\" Holzer says. \"And Lincoln went downstairs early and began receiving guests, and the afternoon comes and goes and African-Americans are gathered in churches, telegraph operators are already keyed up to bring the glorious news to the church whenever it arrived, and nothing happens.\" So why the delay? As Holzer tells it, Lincoln had found a mistake in the handwritten document brought for his signature. The whole thing had to be redone. Back it went to the scribe. It took hours. When the proclamation document finally came back to Lincoln, something strange happened: He picked up his pen and put it down several times. People in the room started to wonder if perhaps he wasn\'t going to go through with it after all. Then he began rubbing the fingers on his right hand. As Holzer explains: \"He said, I\'ve been shaking hands for hours and my hand is almost paralyzed. If I sign the proclamation in a quaking hand even though my whole heart is in it, people will look at my signature in 100 years and think, he hesitated.\" Lincoln massaged his hand a bit longer and then picked up the pen and signed his full name, as he did on official documents. \"Then he looked at the signature — Abraham Lincoln — very proudly and said, \'There, that will do,\' \" Holzer says. \"He had said right before that, if my name ever goes into history it will be for this act. He sensed immediately that he had become one of the immortals.\" One misconception about the Emancipation Proclamation is that once it was signed, immediately all the slaves were free. But that was far from the truth. Some areas of the South that had already fallen under Union control were not covered by the proclamation. Also exempt were the four border states that owned slaves but had not seceded, so nearly half a million people remained enslaved there. In fact, Delaware and Kentucky only freed their slaves after the war, in December 1865, when the 13th Amendment went into effect. And in the Confederate states, freedom came only as the Union soldiers advanced. \"Soldiers were armed with these tiny reproductions of the Emancipation Proclamation,\" Holzer says. \"Lincoln had ordered hundreds of thousands of them printed. Suppose an officer gets to a plantation owner that might not understand what he had to sacrifice: \'Here it is. These guys are free. You\'ve got to pay them or let them go.\' And that\'s how it worked, mile by mile in Southern territory. It\'s a long, slow process. At the end of the war, in 1865, for example, slavery had never ended in Texas.\" On the cover of Holzer\'s book is an engraving that shows a scene from April 4, 1865. It\'s President Lincoln, holding the hand of his young son Tad, as he enters Richmond, Va., just two days after Confederate forces had fled their capital. Jubilant African-Americans toss their hats in the air as they greet him: \"They rushed over to him and cheered and knelt,\" Holzer says. \"And Lincoln famously said — and there were witnesses there — \'Please don\'t kneel to me. You must kneel only to God and thank Him for your freedom.\' ... This was Lincoln\'s real emancipation moment. This was a moment when the Union troops were occupying the capital of the Confederacy. And these black workers were actually, that moment, free under the terms of the proclamation. \"Here is the Emancipation Proclamation in action. ... This was Lincoln acknowledging, after all those years of struggle, with the end finally in sight, that this was going to be a different society, a society of mutual respect and not subjugation.\" But that moment of quiet triumph was fleeting. Just 10 days later, Lincoln was assassinated.