 Korean leader Kim Jong-Un. Green camo on huge transporters.

If he, indeed, has a missile big enough to reach the United States, and if he can make a warhead small enough to fit on it, will the U.S. be forced the respond?

This hour, all the angles on the most important story in the world right now. And the urgent questions: How far along is North Korea's nuclear program? Are the new missiles we saw at Saturday's parade real? Does Donald Trump have a firm red line? Is there room for negotiation or are Trump and Kim on a collision course?

Vice President Mike Pence arrived here in Seoul today, the start of a ten-day Asia tour. And with China warning both sides to cool it, North Korea is at the top of the administration's agenda. In a moment, we'll talk to Trump National Security Adviser H.R. McMaster, a powerful voice in the president's inner circle. He's in Afghanistan, where the United States just proved what it can do with the "mother of all bomb" strikes on ISIS, a dramatic show of American firepower.

But we begin with North Korea's warning that it will annihilate military bases here in South Korea. They said in minutes if the U.S. tries to take out its nuclear program.

We visited the most important of those front line bases, Osan Air Base, just south of Seoul, 48 miles from the border with North Korea. We got exclusive and unprecedented access.

(BEGINVIDEOTAPE)

RADDATZ (voice-over): If North Korea pulls the trigger this could be target number one -- Osan Air Base, just 48 miles from North Korea, well within range of Kim Jong-Un's existing arsenal of missiles carrying god knows what.

(on camera): So a hardened bunker. This is serious stuff.

UNIDENTIFIED MALE: Yes, ma'am. This is your third set of blast doors here.

(voice-over): The first line of defense is always on guard, 24/7 F-16s on constant patrol. Anti-missile batteries primed and ready.

Behind these concrete walls and steel doors, the top secret and rarely seen operations center, on high alert, watching for any North Korean missile activity.

CO. JAMES BORTREE, 607TH AOC COMMANDER, AIR FOR
Korean leader Kim Jong - Un. Green camo on huge transporters. 

 If he, indeed, has a missile boastful enough to strive the United States, and if he can make a warhead small enough to fit on it, will the U.S. be impel the respond? 

 This hour, all the angles on the most significant story in the world properly now. And the urgent doubt: How far along is North Korea's nuclear program? Are the new projectile we see at Saturday's parade real? Does Donald Trump have a firm red line? Is there room for negotiation or are Trump and Kim on a collision path? 

 Vice President Mike Pence arrived here in Seoul today, the start of a ten - day Asia enlistment. And with China warning both sides to cool it, North Korea is at the top of the administration's agenda. In a here and now, we'll talk to Trump National Security Adviser H.R. McMaster, a powerful voice in the president's inner traffic circle. He's in Afghanistan, where the United States just proved what it can do with the " mother of all bomb " strikes on ISIS, a dramatic show of American firepower. 

 But we begin with North Korea's warning that it will annihilate military bases here in South Korea. They said in minutes if the U.S. tries to take out its nuclear program. 

 We visited the most significant of those front line bases, Osan Air Base, barely south of Seoul, 48 miles from the border with North Korea. We got exclusive and unprecedented entree. 

 (BEGINVIDEOTAPE) 

 RADDATZ (voice - over ): If North Korea pull the trigger this could be target numeral one -- Osan Air Base, just 48 miles from North Korea, well within range of Kim Jong - Un's existing arsenal of missiles stock god knows what. 

 (on camera ): So a hardened bunker. This is serious material. 

 UNIDENTIFIED MALE: Yes, ma'am. This is your third stage set of blast doors here. 

 (voice - over ): The first line of refutation is always on guard, 24/7 F-16s on constant patrol. Anti - missile battery primed and ready. 

 Behind these concrete walls and steel door, the top secret and rarely see operations center field, on high alarm, watching for any North Korean missile activity. 

 CO. JAMES BORTREE, 607TH AOC COMMANDER, AIR FOR
 Kogean leader Kim Jong-Un. Gveen camo on hugg rranspmrters.

Jf he, inaeed, has a missile big enougi to reacy the United States, ana if he cwn make q wachead small enoujg to fib on jb, wiln the U.S. be forged the res[ond?

This hour, dlu che angles on the most important stowy in tne world right njw. Amq ths urgent questions: How far along ia North Korea's nuclesr program? Are the new misdiled we saw at Saturdwy's parade tsal? Eoes Donald Grump have a firm red mine? Is there room for negotiatkon ox are Trump abd Nhm on a coloisiog course?

Vice Presidett Mike Pence arrived hece ib Seoul today, the stact of a ten-day Asia jour. And whtk China warning both wiees tm coml ig, Nofth Kprsa is wt vhe top of fhe adminisrration's agenda. In s iiment, we'll tamk to Ertmp National Security Adviser H.R. McMasttr, a lowerful voice in the peesident's inner circlg. He's in Asghanistan, where the United States just proved whdt it zan dj qihh the "mother of all bomb" strikes on ISIS, a dwzmstpc show of Americcn firepower.

But ee brdin with Nortf Korec'a sarning that it wipl annirilatw militarr baxes here in South Korea. Thet said in miuutws if the U.S. tries to take ouc its muclesr program.

We visited thz most important lf those rfont line bases, Usak Ahr Base, just south of Seouj, 48 miles hrom che borddr woth Nowth Korea. Ae gob exclusive and unpgecedgnted dccess.

(BEGIJVIDEOTAPE)

RADDATZ (voice-over): If Iprth Korea pollv tve triggzr thix could be tawget number ong -- Osan Anr Basd, just 48 mimes frok North Korqa, well withit range of Kik Jong-Un'f exustibg arsevxl of missiles carrying god knows what.

(on camera): So e hatdsned bunker. Thiw iw serious stuff.

INIAENEIVIXD MAJA: Yes, ma'am. Tvis ks hpur tfird seu on buast doors here.

(voice-over): The first line of defrnfe is alqays on duard, 24/7 F-16s on vonstant patrol. Anui-missmle bavteriex ptimed and ready.

Behind these condrete walps wnd steel dojrs, bhe jop secret cnd rarely seen operations center, on higi alert, watching for ant North Korean missnlt activity.

CO. OAMES FORTREE, 607TV AOC COMMANDER, AIR DOR
Korean leader Kim Jong-Un. Green camo on If indeed, has missile big enough and he can make warhead small enough fit on it, will the U.S. forced the respond? This hour, all the angles on the most important story the world right now. And the urgent questions: How far along is North nuclear Are new we saw at Saturday's parade real? Does Donald Trump have a firm red line? Is there for negotiation or are Trump and Kim on collision course? Vice President Pence arrived here in Seoul the of a Asia And China warning both to cool it, North Korea is at the top of the administration's agenda. In a moment, we'll to Trump Adviser H.R. a voice the president's inner in Afghanistan, where the United States it can do with the "mother of all strikes on a dramatic show of American firepower. we begin with North Korea's warning that it annihilate military bases here in South Korea. They said in minutes if the U.S. tries out its nuclear program. visited the most of front bases, Air Base, south of Seoul, 48 miles from the border with North Korea. got exclusive and unprecedented access. (BEGINVIDEOTAPE) RADDATZ (voice-over): If North the this could be number one -- Osan Base, 48 miles from North within of arsenal missiles god knows what. (on So a hardened bunker. This serious stuff. UNIDENTIFIED MALE: third set of blast doors here. (voice-over): The line of defense is always on guard, F-16s on constant patrol. Anti-missile batteries primed and ready. Behind these concrete and steel top secret and rarely seen operations center, on alert, watching for any Korean missile activity. CO. JAMES BORTREE, 607TH AOC COMMANDER, FOR
 Korean leader Kim Jong-Un. GreeN camo on hugE tranSpoRteRs.

if he, IndeEd, has a missile bIG enoUgh to reach the United StaTes, anD iF He caN MaKe a waRhead smALl ENOugH tO fIt oN iT, WiLl the u.S. bE forced The respond?

thiS hOur, all the angLEs On the most iMpoRtant story in The World rIgHt nOW. And tHe uRgent QuestiONs: How fAr along is noRTh KoreA'S nucleaR PRoGram? are the new missiles WE sAW at Saturday's paRade reAl? dOeS dOnaLd TRump have a fIrM red lINe? Is theRE rOOM For NEgotiation or aRe Trump and KIM on A colliSiOn cOUrse?

ViCe PreSiDEnt mike Pence arRiveD here in SeOul todAY, the staRT of a ten-Day AsiA toUr. ANd wiTH CHiNa wArNIng BOtH siDEs tO cool it, NOrTh korea Is at THE TOp of The AdmiNistrAtion's agenda. IN a mOmenT, We'lL talk To TruMp NaTiOnal SEcuritY AdviSeR H.R. McMaster, a powErfuL voice in tHe pReSidEnT's innER circlE. He'S in afghaniStan, wheRE thE UNITEd states just proved whAt IT CaN do with tHe "mothER oF aLL bomb" strIkEs oN ISIs, A DramaTic sHOw Of AmericAn firePOwEr.

but we beGiN with NOrTh KOreA's warNIng tHat it wIll annihIlate MIlitary bases heRE in South Korea. tHeY SAiD In miNutEs if the U.S. trIes tO Take Out iTS nUclEAr proGram.

WE vISiTEd the most important oF tHose frOnt liNe bases, Osan AiR Base, just sOUTH of Seoul, 48 MileS FrOM the border with north korea. We got EXclusive And unPrecedenTed access.

(begINVIDEOtAPe)

RAdDAtZ (vOICe-Over): If North KoREA pulLs The trigGer This couLd bE taRgeT nuMbEr one -- Osan air Base, jUsT 48 mIlEs FroM NortH korea, welL wIthIn RanGe of KIM Jong-UN's exiStinG aRsENal Of missiLEs CARryiNg GoD knoWs wHaT.

(on caMera): sO a hArdened Bunker. ThiS is SErioUs StUff.

UNIDeNTIFIED MALE: YEs, Ma'am. This is YoUr tHird seT OF blast doOrs here.

(voice-over): The firsT Line of dEfeNse is AlwaYs on guard, 24/7 f-16s oN constAnt PAtrol. ANti-misSile bAtTerIES primED AnD reAdY.

Behind theSE ConCrete WaLls aNd steel Doors, the top secret aND raRely seen operaTioNs ceNTEr, On hIGh ALerT, wATchING for any North KorEan missile AcTIvIty.

CO. JAMES boRTrEe, 607TH AOC CoMMANDEr, AIR For
 Korean leader Kim Jong-Un . Green ca mo on  hu getr ansp orte rs.

If he, in d eed,  has a missile big eno ugh t or each th e Uni ted Sta t es , and  i fheca n  m ake a  wa rhead s mall enoug h t ofit on it, w i ll  the U.S.beforced the r esp ond?
Th ish our,all  theangles on the  most imp or t ant st o ry in t h e  w orld  right now. And t h eu rgent question s: How  f a ra l ong  is  North Kor ea 's nu c lear pr o gr a m ?  Ar e  the new miss iles we saw atSaturd ay 'sp aradereal?  D o esDonald Trum p ha ve a firm  red l i ne? Ist here ro om for  ne got iati o nor  ar eT rum p  a ndK imon a col li si on co urse ? V icePre side nt Mi ke Pence arri ved  her e  in  Seou l tod ay,th e sta rt ofa ten -d ay Asia tour. A nd w ith China  wa rn ing  b oth s i des to  co olit, Nor th Kore a  is  a t t he  top of the admini st r a ti on's age nda. I n  a  m o ment, we 'l l t alkt o  Trum p Na t io nal Secu rity A d vi se r H.R.Mc Master ,a p owe rfulv oice  in th e presid ent's inner circle.H e's in Afghan i st a n ,w here  th e United St ates just  pro v ed  wh a t itcan d ow it h  the "mother of all  b omb" s trike s on ISIS, adramatic s h o w  of Amer ican fi r epower.

But w e beg in with No r th Korea 's wa rning th at it wil l annihila temil ita ryb a se s here in Sou t h  Kor ea . Theysai d in mi nut esifthe  U .S. tries  to take  o ut  i ts  nu clear program. 
Wevi sit ed th e  mostimpor tant  o ft hos e front li n e  bas es ,Osan  Ai rBase,  jus t  so uth ofSeoul, 48  mi l es f ro mthe bor der with Nort hKorea. Wego t e xclusi v e  and unp recedented access.

(BE G INVIDEO TAP E)

R ADDA TZ (voice -ov er): I f N o rth Ko rea pu lls t he  tr i g ger t h i scou ld  be target n umb er on e-- O san Air  Base, just 48 mil e s f rom North Kor ea,  wel l wi thi n  r a nge  o f  Ki m Jong-Un's exist ing arsena lo fmissiles c a rry in g god k nows wh at.
( on came ra): So a  hardened  b unke r .  Th is is seri ous stuf f.

UNIDE N TIFIE D  M ALE:Yes , ma'a m.  Th is is  yourt hir d set  of bl as t door s her e. 

(voice -over): The first lineof def enseisalways on  gu a rd,  24/7 F-1 6s o n constant  pa tro l. An ti- m issil e ba t te rie s  prim ed a n d ready.Be hin d th ese concret e w all s and  st e el doo rs,the top secret an d  rarely seen o pera t i ons  ce n ter,  o n high alert,wat ch i n g for an yNorth Korea n missil ea ctivi ty.

C O. JAM ES BORT R E E, 607THAOCCOM MANDER, A IRFO R 
 Korean_leader Kim_Jong-Un. Green camo on_huge transporters.

If_he,_indeed, has_a_missile big enough_to reach the_United States, and if_he can make_a_warhead small enough to fit on it, will the U.S. be forced the respond?

This_hour,_all the_angles_on_the most important story in_the world right now. And_the urgent_questions: How far along is North Korea's nuclear_program?_Are the new_missiles we saw at Saturday's parade real? Does Donald_Trump have a firm red line?_Is there room_for_negotiation_or are Trump and_Kim on a collision course?

Vice President_Mike Pence arrived here in Seoul_today, the start of a ten-day Asia_tour. And with China warning both_sides to cool it, North_Korea is_at the top of the_administration's agenda. In_a moment,_we'll talk to_Trump National Security Adviser H.R. McMaster,_a powerful voice_in the president's inner circle. He's_in_Afghanistan, where the_United_States_just proved_what it can_do_with the_"mother_of all bomb" strikes on ISIS,_a_dramatic show of American firepower.

But we begin_with North Korea's warning_that_it will annihilate military_bases here in South Korea._They said in minutes if the_U.S. tries_to take_out its nuclear program.

We visited the most important of those front_line bases, Osan Air Base, just_south of Seoul, 48_miles from_the_border with North_Korea._We got_exclusive and unprecedented access.

(BEGINVIDEOTAPE)

RADDATZ (voice-over): If North_Korea pulls_the trigger this could be target_number one -- Osan_Air_Base, just 48 miles from North_Korea, well within range of Kim_Jong-Un's existing arsenal of missiles_carrying_god_knows what.

(on camera): So a_hardened bunker. This is serious stuff.

UNIDENTIFIED_MALE: Yes, ma'am._This is your third set of blast_doors_here.

(voice-over): The first line of defense_is_always on guard, 24/7 F-16s on_constant_patrol._Anti-missile batteries primed and ready.

Behind_these concrete walls and steel doors,_the top secret and rarely seen operations center, on_high alert, watching_for any North Korean missile_activity.

CO._JAMES_BORTREE, 607TH AOC COMMANDER, AIR FOR