CNN Moderator: Our guest, John Lewis Gaddis, is a professor of history at Yale University and the author of numerous books on the Cold War - including, most recently, "We Now Know: Rethinking the Cold War."

CNN Moderator: What was the single most important factor in the outcome of the Cold War?

John Lewis Gaddis: Well in some ways you could argue that economic disparities were the single most important factor, because in the end it was largely economic capabilities that determined the outcome.

Chat Participant: If the British and U.S. representatives had put their foot down, would Stalin have received as much land as he did?

John Lewis Gaddis: Probably would not have made a great deal of difference. The problem was that the British and Americans at that time were not really in a position to put their foot down because they did not have their troops in position where this would have made a difference.

Chat Participant: Is it true we could have entered Berlin first but waited for the Soviets?

John Lewis Gaddis: Well it's not true that we could have entered Berlin first. That seems unlikely because of the way that the armies were entering Germany. At the same time, it was never our intention to enter Berlin first. Eisenhower's strategy was to advance on a broad front, and entering Berlin first was never a major American military priority in the first place.

CNN Moderator: Did nuclear weapons really keep the peace?

John Lewis Gaddis: Lots of historians think that nuclear weapons really did keep the peace -- it's even been suggested the atom bomb should have gotten the Nobel Peace Prize!

Chat Participant: Had it not been for the U.S. and NATO, what other nations would have become Soviet satellites?

John Lewis Gaddis: There's a good chance that if the U.S. hadn't launched the Marshall Plan and then NATO, France, West Germany, Italy and possibly other parts of Europe might have become Soviet satellites -- not because the Russians would have invaded, but because the people of these regions might voluntarily have chosen to elect communist parties subservient to Moscow.

Chat Participant: When did the leaders realize they had a Cold War on their hands?

John Lewis Gaddis: Most historians think the U.S. realized this early in 1946. But Stalin may well have been thinking in terms of a Cold War all along.

CNN Moderator: What single individual was most responsible for the Cold War?

John Lewis Gaddis: It's hard to pick a single individual for something as complex as this. But if I had to choose, it would be Stalin -- he made the greatest difference -- and the outcome would have been greatest if he hadn't been on the scene.

Chat Participant: Did Churchill's Iron Curtain speech at Westminster College have an impact on the Cold War?

John Lewis Gaddis: It probably did, in the sense that the Stalin we know reacted very negatively to it. But Churchill made the speech because he himself was convinced the Cold War was already under way.

Chat Participant: What would you say is the single most interesting, important and surprising document to emerge from the communist archives -- and why?

John Lewis Gaddis: Tough question -- there are lots of documents and there have been lots of surprises. Maybe the biggest surprise is one that comes from reading many of these documents, not just a single one. It's that the Soviet leaders took their own ideological rhetoric as seriously as they did. They actually seemed to believe their own propaganda.

Chat Participant: What was the largest mistake, in your opinion, that the U.S. made during the Cold War?

John Lewis Gaddis: That's an easy one for me. It was getting involved in an unnecessary, costly and tragic war in Vietnam.

CNN Moderator: What single individual do you think was most responsible for ending the Cold War?

John Lewis Gaddis: No question on this one -- Gorbachev -- and history will regard him a lot more favorably than the Russian people currently do.

Chat Participant: Professor Gaddis, do you think that if the atomic bomb had been ready in time, it would have been used against Nazi Germany and what impact would that have had on the Cold War?

John Lewis Gaddis: Yes, if the bomb had been ready in time, it almost certainly would have been used against Germany. Remember how easily we flattened German cities with conventional bombs. The impact on the Cold War, I think, might have been even more severe than the use of the bomb against Japan, because for the Russians it would have been closer to home.

CNN Moderator: What could the West have done to end the Cold War sooner?

John Lewis Gaddis: That's a good question, and historians are going to be debating it for a long time. Some historians think tougher policies earlier -- Reagan-like policies, for example, in the 1970s or even 1960s, might have had this effect. Other historians warn that such policies would have been very dangerous. In the end, probably events inside the U.S.S.R. were the most important in determining when the Cold War ended.

Chat Participant: Do you think, in the long term, that nuclear weapons will keep peace?

John Lewis Gaddis: I wish I knew! It's a very different ball game when you're talking about lots of nuclear powers, as opposed to just two big ones, as during the Cold War. When you come right down to it, the Russians and the Americans were pretty rational in the way they handled these things. Others may not be.

CNN Moderator: Will Russia's current economic crisis spur the comeback of communism?

John Lewis Gaddis: It's worth remembering that economic crises in the early 20th century had a lot to do with the coming of communism in the first place. The situations are obviously different now, and communism isn't going to come back in its Stalinist form. Capitalism, however, isn't very popular in Russia just now.

Chat Participant: Who was the most influential leader during the Cold War?

John Lewis Gaddis: It would be hard to pick a single most influential leader if one is talking about the entire Cold War. Stalin, for sure, at the beginning; Gorbachev at the end. But during the middle, it's more complicated, and surely the Americans -- Truman, Ike, JFK, and certainly toward the end Reagan -- were very influential.

Chat Participant: Why did the Western powers simply do nothing during the Prague Spring?

John Lewis Gaddis: Pretty much for the same reasons they did nothing, as you'll see on the tapes, during the East Berlin uprisings of 1953, or the Budapest rebellion of 1956. There didn't seem to be any way we could use force to prevent the Russians from regaining control without setting off an all-out war.

Chat Participant: Do you believe that Stalin was mentally/emotionally unstable?

John Lewis Gaddis: Stalin's biographers have wrestled with this question. He surely wasn't "normal"! Most of them would agree that, at a minimum, he suffered from paranoia. Most paranoids, though, don't leave behind as many bodies as he did.

Chat Participant: But wasn't action in Vietnam consistent with our long-term Cold War strategy of containment; in other words, we had to go there as tragic as it was.

John Lewis Gaddis: Our policy-makers thought it was, yes. But was Ho Chi Minh the same kind of enemy Stalin had been? Was Vietnam as crucial a strategic area as Europe or Japan? Looking back on it all now, it's clear that they weren't. And that pretty quickly became clear to critics of the war at the time.

CNN Moderator: Helmut Kohl was voted out of office today - what will be his legacy as among the last of the Cold War leaders?

John Lewis Gaddis: Kohl's legacy will be that he presided over the reunification of Germany in 1990. Few people, even a year earlier, thought that would be possible by peaceful means. Kohl, however, together with George Bush, will get the credit for having pushed this through, and for having persuaded Gorbachev to accept it.

Chat Participant: Many historians take great pains to emphasize the mutual guilt of both the U.S. and the U.S.S.R., but in your opinion, aren't those historians stretching it, and can't we truly say this was a simple case of good versus evil?

John Lewis Gaddis: It's hard to take good versus evil out of it -- not because historians necessarily should judge everything in these terms, but rather because ordinary people at the time -- you'll see them in the tapes -- looked at it in these terms.

Chat Participant: Did the Soviet-Chinese split in 1962 change U.S. policy dramatically?

John Lewis Gaddis: No, indeed the U.S. was very slow to respond to the Sino-Soviet split. Publicly, the change really doesn't come until Kissinger and Nixon go to Beijing in 1971-72. Behind the scenes, though, we know that as early as 1963 we were quietly talking with the Russians about the possibility of jointly nuking the Chinese nuclear test facilities. So there's a difference here between what happened in public and not in public.

Chat Participant: To what extent did the decision to drop the bomb set the tone for the Cold War? How different would the postwar years have been had the bomb not been dropped on Hiroshima?

John Lewis Gaddis: I don't think the postwar years would have been too much different had the bomb not been dropped. Stalin was going to distrust the West in any event -- as you saw in tonight's episode when he bugs FDR at Tehran. I do think the bomb increased Stalin's suspicions, though -- and paradoxically, it probably made him less willing to negotiate, if only to show he hadn't been intimidated.

Chat Participant: Was there anything that you found that, in your opinion, could have prevented the Cold War from happening?

John Lewis Gaddis: The more I look at this, the more I think some kind of Cold War was unavoidable -- given the nature of the two ideological systems. The fact that Stalin was in charge of one of them, though, made things worse than they might have been.

Chat Participant: Should there be a new "Marshall Plan" to keep Russian scientists from selling their expertise to terrorists?

John Lewis Gaddis: The Marshall Plan worked so well that, these days, when anything goes wrong, people say there should be a new Marshall Plan. Certainly it would make sense to try to think about how we can keep the Russian economy from imploding. It's interesting to consider that the Dow dropped 500 points the other day when the Russian ruble collapsed. Ten years ago, it might have risen 500 points. It's a new world.

Chat Participant: Mr. Gaddis, when do you think the world came closer to World War III -- during the Cuban Missile Crisis or the Yom Kippur War?

John Lewis Gaddis: Everybody would agree that the Cuban Missile Crisis was the most dangerous moment. What's interesting are the arguments about what was the second most dangerous moment. Some would say the Berlin crisis of 1961, others the Yom Kippur War of 1973. My own choice is an episode few folks have even heard about, although you'll see it treated toward the end of the series. It's the Abel-Archer NATO exercise of late 1983, when a NATO war game spooked the Russians so much that they thought the U.S. was about to launch a first strike.

Chat Participant: By expanding NATO, does the U.S. appear to be shoving the result of the Cold War into the Soviet face?

John Lewis Gaddis: Well, that's certainly how most Russians I know see it. It's a very good question why we should be expanding NATO now that the Cold War -- which NATO was created to fight -- is over.

Chat Participant: Has a body count been established for the Cold War?

John Lewis Gaddis: Body counts are very problematic things, and as far as I know, there's no one definitive figure. It depends on what you count -- if Mao's victims from the Great Leap Forward famine of 1958-61 are included, that's 30 million right there. No other Cold War episode was nearly as costly as this one was, and of course this is one we hardly heard of at the time.

Chat Participant: When was it clear the Soviets would lose?

John Lewis Gaddis: It was pretty clear that the Soviets weren't going to win by the late 1950s. But it was not at all clear that they would completely collapse until just about the time that happened -- the late 1980s.

Chat Participant: Do you think the Cold War really ended or is it only a short break on both sides?

John Lewis Gaddis: Sure, the Cold War as we knew it -- as a geopolitical/ideological rivalry between the U.S.S.R. and the U.S. -- is over. But that doesn't mean the world is free from international tensions, from cold wars of other kinds, and perhaps a few hot ones as well.

CNN Moderator: Any final thoughts Professor Gaddis?

John Lewis Gaddis: Thanks to all who participated, and thanks to CNN for coming up with the idea for this series.