Over the course of the Civil War, more than 600,000 lost their lives in just four years. In order for America to survive and reunify as a nation free for all, it would need extraordinary leaders to emerge above the rest.

Enter Abraham Lincoln and Frederick Douglass—their relationship spotlighted in "Fox & Friends" co-host Brian Kilmeade’s new book, "The President and the Freedom Fighter," and an accompanying Fox Nation special out Nov. 7.

The special, based on Kilmeade’s book of the same name, brings to life a nearly-forgotten piece of history and shows how Lincoln and Douglass’ friendship changed each other and made America free for all.

"I wanted to focus on how they intersected where we were as a country then: never perfect, always trying to be," Kilmeade told Fox News’ Tucker Carlson Tuesday night.

BRIAN KILMEADE: AMERICA'S WAR ON AMERICAN HISTORY

"And I just think that some of the race problems that we have today is [sic] because people have no idea how far we've come," he continued.

Both men had the odds stacked against them. Lincoln was born to illiterate parents in abject poverty, with only one year of formal education; setting him apart as a presidential candidate.

As tough as Lincoln's first 14 years were, though, Kilmeade acknowledged Frederick Douglass had it far worse.

Born as a slave who escaped for his freedom, Douglass wasn’t satisfied until every person was free. He continued his self-education, was mentored by esteemed abolitionists, wrote a bestselling biography, started a newspaper and became a lecturer known around the world.

"He wanted to make his stand here, almost in biblical terms," historian Douglas Brinkley tells Kilmeade. "He saw the promise of America, which is hard to do when you're being beaten. So Douglass' gift was he never let the slave owners own him."

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In the 1850s, the men rose in stature as America diverged on the issue of slavery. When Lincoln was elected and didn't immediately free the slaves and messaged appeasement in exchange for reunification, Douglass seethed.

"Douglass actually wanted Lincoln to pick up the pace and have the emancipation quicker," Kilmeade said. "Lincoln had to take his time, the country wasn't ready. When it was, when they came together, they were a force."

"The whole story is that progress takes patience," Sen. Tim Scott, R-S.C., tells Kilmeade in the special.  "Douglass should have been rightfully so angry at the lack of progress, pushing Lincoln to move as quickly as possible. But at the same time, you have to admire, respect Lincoln's patience."

"The President and the Freedom Fighter" book is in stores now. Subscribers of Fox Nation can watch the accompanying special on Sunday, Nov. 7.

Fox Nation programs are viewable on-demand and from your mobile device app, but only for Fox Nation subscribers. Go to Fox Nation to start a free trial and watch the extensive library from your favorite Fox News personalities.

Fox News’ Kelsey Koberg contributed to this report.