Gorbachev, who met with Correspondent Dan Rather, was the last general secretary of the Communist Party of the Soviet Union.
"Mr. Gorbachev, tear down this wall," said President Reagan in 1987, challenging his Soviet counterpart.
In Berlin, they were two men in the middle of a Cold War, trying to find common ground.
"This was a difficult road. But we traveled that road. We started the elimination of nuclear weapons. We prepared conditions to end the Cold War," says Gorbachev.
When Gorbachev met with the former president in 1985 in Geneva, did he think at the time that Reagan was a mortal enemy of the Soviet state?
"I don't think that he regarded me as a personal enemy," recalls Gorbachev. "We looked each other in the eye very closely. And that is something that means a great deal. And I felt some spark of hope."
It had been six years since leaders from the two superpowers had met. And when the negotiations began, both sides took the hard line.
"We started with recriminations and accusations. And it was difficult to hope that the outcome would be positive," says Gorbachev.
Reagan, the fierce anti-communist, the man who coined the phrase "The Evil Empire," became the American president who found a Russian partner to pull the world away from the brink of nuclear war.
"Two days later, we issued a common statement that said a nuclear war can not be won and must not be fought," says Gorbachev.
The first important step had been taken, and the two men who had their fingers on the nuclear trigger, shook hands.
And then, says Gorbachev, there was Reykjavik, "which was a big step." There, they met for two days -- sometimes with advisors, sometimes just the two men alone with translators.
"And even though those two days were not crowned with an agreement, we saw that there was a chance to move forward," says Gorbachev.
Their work, the dialogue, and the growing friendship led to a historic treaty in which the nations agreed for the first time to actually destroy nuclear weapons -- effectively ending the arms race.
"We signed the agreement. We exchanged pens. I still have that pen as a memento," recalls Gorbachev. "And the process was under way. A process that was very promising."
Later, there would be trips to New York for Gorbachev, and to Moscow for Reagan.
"The General Secretary and I have one idea in common -- that there must be friendship between our two countries," Reagan said during his 1988 visit to Moscow.
Like the friendship shared by these two men, it was a bond that lasted years after they had both left office.
"Ronald Reagan's life is over. His earthly life is over," says Gorbachev.
"We should see that at a time when the world was in great danger, perhaps nuclear war ... this person measured up to the challenge of history."