[ cheers and applause ] this is "nightline." >> tonight, talking tough. >> rocket man is suicide mission for himself and his regime. >> president trump and his first address to the u.n., vowing to totally destroy north korea if the u.s. is forced to defend itself. in the air above south korea with the f-16 pilots always prepared for the unimaginable. >> best way to prevent a war. >> plus, bob woodward on the tyranny. the boundary between north korea and china. >> look at this warning. do not converse or exchange objects with people on the other side of the border of the will. >> a view from the ground. >> i don't think you see those

plows much anymore. >> and the notorious regime clamps down at a check point. but first the "nightline" five. ♪ the best things in life they're free ♪ ♪ stars belong to everyone ♪ ♪ they cling there for you and for me ♪ ♪ flowers in spring ♪ th r tling there for you and for me ♪ ♪ the sunbeams that shine ♪ they're yours and their mine

♪ love can come to everyone ♪ the best things in life they're free ♪ ♪ good evening. thank you for joining us. tonight another escalation in the war of words between

president trump and north korean dictator kim jong-un. this time with the leaders of the world watching. the president's first address to the united nations. so what comes next? we go inside the brutal regime. >> a war of words across the pacific. >> details about north korea's missile launch -- >> north korea claims it has successfully tested a hydrogen bomb. >> north korea has fired off another missile. >> and a show of force from both sides. >> he has said things are horrific. with me he's not getting away with it. >> escalating tensions between the and u.s. north korea on extraordinary heights in recent months. >> they will be met with fire and fury like the world has never seen. >> and this morning at the u.n. general assembly -- >> if it is forced to defend itself or its allies, we will have no choice but totally destroy north korea. >> president trump singling oorn

one of the most high stakes foreign policy speeches of his presidency. >> rocket man is on a suicide mission for himself. and for his regime. >> leaving many to fear that the incendiary rhetoric is choking what reminds left on the road to diplomacy and that one faus move could tip the balance. >> what worries me is the possibility of misinterpretation that leads the catastrophe that no one wants. >> we spent time with the u.s. air force last month on osan air base in south korea. witnessing some of the u.s. military's most advanced war planes. >> layser to target line.

265 to 295. >> we are given a unique look into the front lines flying on f-16. >> we're going to get approval the move closer. >> approval hard to come rebyin area known as the 8. e p-prohibited, a highly restricted space between koreas. >> so how far are we? >> right now, 10 miles. >> and that's as close as you can get? >> that's as close as we can get. >> so we're not really in a war zone but it can happen at any time. >> that's our mission. we like the say that we're ready to fight tonight. >> back on the ground. i spoke to captain daniels and his fellow pilot major graham

weller who told me all these preparations are in fact on avoid war. >> the best way to prevent a war is to make sure the north korean regime knows if they were to initiate a conflict on this peninsula, they would lose as quickly. >> if ultimately our effort to did heter then phase, then we're manitobaizing to defend the south koreans and their way of . sfelio it's only 35 miles fro the border. >> kids is that shopping. >> the seoul bureau chief who likes everyone here lives with uncertainty. >> this time, doesn't it seem different? >> it does. that's because we have a north korea so close to the finish line on a nuclear tipped icbm that can reach the u.s. >> the potential range of north korean missiles has multiplied in recent years. in july north korea shot a

missile,300space, landing in the sea of japan. but experts say angled with a different trajectory, it could have reached deep into the united states. >> the kim regime seeps will to have had a very comprehensive plan for the way they want to move forward. >> they said it comes from advances in rocket engines. a technology north korea likely acquired outside its borders. >> most likely the for thatter soviet union. >> and many fear kim's thirst for nuclear weapons to put on those missiles is not going away. >> his primary objective is to hin a nhearr. fsee weapons capability is the most assured way to keep and maintain hisehd jong-un remains something o an enigma of the will the third son, he rose to power in 2011

following his father's death. experts believe he is in his early to mid 30s and that he nt to school in switzerland before returning to north korea. >> he was being grouped from about age 8. this is a young man brimming with confidence. has almost never been told no of the. >> kip has ratcheted up the weapons program, conducting more missiles in the six years he's been in power than his father and grandfather combined. these tests rocking a delicate balance of power north korea has the ability to attack south korea and japan of countries the u.s. has sworn to protect. aided by america's arsenal of nuclear weapons. >> he clearly wants a weapon that will did heter the united states and other outside powers from entintervening and overthrowing his jeel.

>> he traveled the border between china and north korea. >> so this is china. right across the river is north korea. and it is absolutely dark. >> a country he's been to many times. always the capital,, always under the watchle have eye of the government. >> this drones flying over the border. and look at this warning. do not converse or exchange objects with people on the other side of the border. they told us to be careful. >> barbed wire, rivers, bridges separating them. >> we're just heading south. heading to what is called the new district. this is where a brand new bridge is under construction for the last seven years or so. but it is almost stopped. slowing down. >> this $350 million project was built by the chinese. it now sits as bridge to nowhere. literally. satellite pictures show that the

bridge abruptly ends on the north korean side in a dirt field. bob meets a truck driver who used to trade with north korean farmers and most recently helped in the construction of this bridge. >> kim jong-un is testing so many nuclear bombs and missiles. is there much fear here? >> translator: journey along the border, a glimpse so few have seen. >> i don't think you see those plows much anymore. >> there's on tshi c naside. and there's north korea on the other. >> you see the difference wealth. >> here the team is stopped at a check point. forced to turn around. >> he's looking through all of our bags. >> the guys are following us. >> will they be following us from now on? who snngs we'll try a different route back to the border. clearly it is getting more difficult. >> back in south korea, lee who

there, says orth korea and kim's threats against the u.s. are empty. lee began launching balloons containing leaflets north, hoping, he says, to open the eyes of north koreans to the deception of their leader. something he experienced himself. >> what do you think their life is like now under kim jong-un? >> for now the two leaders continue their while the u.s. military continues to train for the real thing. for "nightline," seoul.

ks our . and foanrth more of bob's journ watch the full abc news documentary, an invent border where china meets north korea at abc news.com/features or by downloading the abc news app. and next, how ten minutes at a studiieoo the attention of the world. when you're close to the people you love, does psoriasis ever get in the way of a touching moment? if you have moderate to severe psoriasis, you can embrace the chance of completely clear skin with taltz. taltz is proven to give you a chance at completely clear skin. with taltz, up to 90% of patients had a significant improvement of their psoriasis plaques. in fact, 4 out of 10 even achieved completely clear skin. do not use if you are allergic to taltz.

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♪ see you again >> the most viewed music video on youtube for nearly a month composed thor lyrics during a meeting. he said it took only a matter of minutes. >> my friend passed away in 2012. the moment i found out he was no longer living. i texted his friend. i was like, see you soon. how about see you again. it's been a long day without you my friend and i'll tell you all about it when i see you again. i think i had in the span of 30 minutes, all executives walking into the room of who will is this kid? he just cracked the code for the end of this really important scene for fast and furious. no one has been able to do it. he nailed in it ten minutes. i'm supposed to be like i had no idea. ldknew the songou w life. i knew it. >> it has all gotten a little crazy for charlie. >> this is it. this is where the magic happens.

>> this is magical blue bus.bu >> he spends a lot of time on there bus. >> very posh. this nice fake leather. >> but he takes his studio with him on the road. >> i've interviewed other art i haves and i have not seen the tour bus studio. >> many start right here on his iphone. >> every song was made off the phone just from ideas. >> those ideas snow ball when his virtual one man band gets to work. >> you know my song, attention, this one started in tokyo of it popped into my head. like those owed cartoons where a mouse iss sneaking across the kitchen floor. and the next thing i did was add these cool little chimes. thes cane intt tlethings.

some glasses and cans together. and they sound kind ofut they went perfectly with this little base part. and the final thing, anything that makes you do this. like you just -- it makes you just do it. you puthe i'm on my tour bus. bus. >> he may look the part of a pop star. >> so your mop wm was completel influential. >> yeah of she taughte m at 4 years owed. my mom said, i would be walking around. mom, the wind is blowing. i always had it but it became very apparent to me when i was around 8 years owld.. i

karm enters and play it. >> he first reached internet fame with youtube. ♪ ♪ you just want attention >> now recognition goes wherever he goes. >> today he fits in fan meet and greets. in between sound checks. charlie has plenty of hits to his name. marvin guy. ♪ superman >> t one call away. ♪ i'm only one call away >> but he says he's still driven to put on a one of a kind show for these fans. who is on your shirt?

charlie puth? you're all here to see charlie? okay. >> nerves are good. yes. >> writing a soundtrack. >> okay. it is packed now! finally, it is time to take the stage. ♪ you just want attention ♪ ♪ you don't want my heart ♪ >> the atmosphere is electric. the energy is out of control. if charles gets his wish -- ♪ it's been a long day ♪ i'll tell you all about it when i see you again ♪

>> the takeaway is inspirational. for that next artist somewhere in the crowd. >> my hope after the album is out, rather than reading all the reviews and knowing what people hink of it.raerheead vei rsionul of me than brand ne version of me. i want them to hear that album and try to beat it and i want them to be expired by it. that means the most to me. ♪ >> for "nightline," gloria river ar a in washington, d.c. next, we're tracking hurricane maria on its way to

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finally, we are hurricane maria barreling toward puerto rico. the category 5 storm with sustained winds of 175 miles an hour has already wreaked havoc in the caribbean. the governor of puerto rico twarng storm could hit the violence and force that we haven't seen here for several generations. we will continue to monitor the situation throughout the night and on gma in the morning. thank you for watching abc news. and on gma in the morning. thank you for watching abc news. as always, we're online at abc food. water. internet. we need it to live. but what we don't need a surprises, like extra monthly fees. i see you, fee, played by legendary actress anjelica huston. you got me, mark. we just want fast internet for one, simple rate. for all the streaming and the shopping and the newsing, but most of all... for the this. internet for one everyday simple price and no extra monthly fees.