Transcript for As historic Singapore summit begins, some South Koreans have 'high hopes'
There you see Kim Jong-un and South Korea's moon jae-in paving the way for this week's summit. They are the two leaders with the most to gain and the most to lose this week. North Korea hopes for the kind of prosperity they see in the south. South Korea fears catastrophe if war breaks out. Martha Raddatz traveled there this week for a closer look at what's at stake. Reporter: It's been six months since we took the one-hour from South Korea's capital beyond the guard towers. The barbed wire barriers that divide the once unified nation roughly in half. And there it is. North Korea. From this observation tower along the 160-mile long 2 1/2-mile-wide demilitarized zone, the view of the north is breathtaking. Last time I was at this observation point where you can look right over there, it was a time of great tension. Great fear for south Koreans that somehow they were on the verge of war. This time, it just feels very different. Young children explore the grounds. Families peer through binoculars to get a look at the neighboring country in which the south is still technically at war. This father tells us that with the approaching summit and possible peace, he wanted his children to see North Korea with their own eyes. A potential catastrophe for which the U.S. Military had to constantly prepare. From the land. So a hardened bunker. This is serious stuff. Yes, ma'am. Reporter: To the seas. To the skies. So how far are we from north Korea? Right now, ten miles. That's as close as you can get? That's as close as we can absolutely go. Reporter: The military threat seems like a distant past. The harsh words yesterday's story. Flash forward to today. Did you ever imagine during the period when president trump was calling Kim Jong-un little rocket man or comparing the sizes of nuclear buttons that we would be where we are now? No, actually, it's a big surprise. Reporter: Kenneth Choi is the chief editor of one of south Korea's major newspapers. Now, the question is will North Korea really go through this denuclearization process? Reporter: It's impossible to answer. This professor who has taught in South Korea for the past eight years, says watching Kim Jong-un on the world stage, have been eye-opening. We know so much more of what makes him tick. What he wants. We would be fools if we were not re-evaluating our understanding. Reporter: And for the young people of south Korea who have never known a unified Korean peninsula, they see an opportunity as well. Kim initiated it. Kim crossed the border. Kim asked for taking a picture together with president moon. I think it's because he seeks to gain legitimacy. Reporter: Tell me what you learned growing up or in school, particularly, about reunification. Well, when I was in the elementary school, there was a song called "Unification is our hope." Our, like, our dream is the reunification of the Korean peninsula. And Martha is back here with Jonathan Cheng, the Seoul bureau chief of "The Wall Street journal." Also want to bring in Bob woodruff, who is in Seoul today. What is the mood like there as we head into the summit? It's pretty good right now. There are some doubters out here. That is true. As you heard from the young people with Martha, most told me they are excited that the summit is taking place. No dangerous downside, they say. They have been living with this conflict for 65 years. They all admit Kim Jong-un and Donald Trump are equally unpredictable. They don't believe shaking hands and talking in Singapore could make it any worse. Probably better. Last night, we took to the streets here in Seoul, where a few hundred people matched in the rain, right in front of the U.S. Embassy. And this is what they want. First, the Korean war to be declared over. It ended in 1953. Not officially. No peace agreement. They want a signed treaty. Second, they want North Korea to denuclearize. Dismantle all of the nukes, not just the long-range ones that could hit the United States. All of it. Those that could hit south Korea, Japan, any other country in the region. No one wants a resolution more than south Korean president moon jae-in. We have to remember, Korean cultures have more patience than ours. People here in Seoul don't expect a quick fix. They believe this summit is the beginning of something they never expected. George? Thank you, Bob. We'll come back to you later this week. I want to pick up on a point Bob made. We have talk a lot. About Kim Jong-un and Donald Trump. Moon jae-in really moved this process. Yes. He was elected, came into office last year in may. Think about the context back then. We were having missile tests. Fire and fury a few weeks later. That was the context in which he came to office in South Korea. He's been pushing and advocating dialogue with North Korea for a long time. That was a tough sell back in that environment because it didn't look like talks were anywhere near. How much of it was -- fear and fear on two different fronts. Fear that president trump would take military action if it came to that? And fear that he talked about at times of pulling U.S. Troops out? Right. Well, I think certainly around August, September last year, if you can bring yourself back then, there was a genuine concern in Seoul, in South Korea, there would be a military option. We saw that earlier this year with the talk of a bloody nose. Throughout the campaign and coming into his presidency, Donald Trump has talked a lot about why do we have all these 28,500 U.S. Troops in south Korea for any way? He managed to concern people on the left who don't want a war. And people on the right who don't want the U.S. Presence to be gone either. I think what Donald Trump has done with a lot of his rhetoric is he's really concerned people on both ends of the spectrum. Raenldly what you had to see with moon last year, moving to the center. We need to be tough on north Korea. We saw Kim Jong-un earlier in the year say, I might be open to talks. Moon jae-in was able to snap into action and go back to his natural position. Which is let's get talks going. And it also focused the minds, as if they needed any more focusing, the minds of the U.S. Military leaders on the Korean peninsula. You saw those images. I remember so well going to those exercises. Being in the fighter jet. Listening to the U.S. Military and how serious this was. How deadly serious this was. They were holding secret meetings all the time. Updating plans. What would happen if North Korea responded? If we attacked first? If we had to attack first? If the U.S. Felt threatened? You heard Donald Trump talk about that. If they aimed missiles at Guam. Remember that. They were planning for this. If something happened, they knew that the U.S., not just south Korea, the U.S. Would take a lot of casualties. Right away. And they wanted to do everything they could to avoid that. On the opposite side, such prosperity across South Korea. In Seoul. How much of an impact does that have? It's so hard to know. Do you thing that any of that bleeds through to north Koreans? Do nay know what is going on in South Korea? Because of the technology, with USB thumb drives, the internet, cellular technology, with people in China. They are increasingly aware of what life is like this south Korea. It forces a stark choice. Kim Jong-un, the possibility of opening up comes part and parcel with these talks. That is a question you don't hear addressed so much. Can the north Korean system, could it absorb the influx of information? Even more -- And could the regime survive that? That's right. And unification? Is that something worth talking about? Or sit just so far in the future that it's not conceivable? Well, in both Koreas, you hear unification talked about adds the ultimate goal. You hear that under conservative and liberal presidencies in South Korea. Increasingly, there's a sense that it's more lip service than anything. You have a generation now that -- once moon jae-in's generation passes out of power here, you'll have people that truly have no recollection of what a unified crow Ya is like. I asked those kids. Tell me what your parents have told you about the war. They all said in that way, my grandparents have said this and
This transcript has been automatically generated and may not be 100% accurate.