near future north korea regime brink collapse rumor swirl palace coups force side world militarize border heighten alert u.s. military face much big problem somewhere pacific north korean submarine believe carry nuclear warheads missiles deliver nobody know sound like plot hunt red october -style technothriller pyongyang technicians continue current pace experts say become ever likely one thing certain north korea plow considerable resources build nuclear capability clearly make progress even tuesday fail missile test show still long way go japanese officials say appear conventional musudan rocket theoretically ability reach japan u.s. territory military base guam explode either shortly leave launcher north korea estimate 20 30 missiles first deploy 2007 yet launch successfully north korean leader kim jong un want analysts believe simple rocket fire nuclear warhead least regional target ultimate ambition however able hit u.s. cities west coast likely submarine could hide sea north korea steadily improve rocket also carry conventional explosives decades detonate first nuclear device 2006 experts believe yet build one small enough place missile credible ability get missiles sea could take well decade perhaps considerably happen however strategic game changer bad u.s. cities west coast would deal prospect however remote might strike north korean atomic weapon least north korea arm nuclear submarine would hugely complicate calculus u.s. president handle crisis korean peninsula course exactly plan fact pyongyang conduct many test year experts believe suggest kim push scientists hard ever deliver work rocket warheads north korea believe tag expertise russian cold war-era scientists capabilities front lag well behind establish nuclear state russia china already believe well ahead iran april south korean u.s. officials say north korean submarine successfully launch ballistic missile travel 18 miles major step forward technical experts say tv footage appear show solid fuel rocket successfully launch underwater essentially system use western force achieve goal testify senate arm service committee april incoming head u.s. northern command responsible defend mainland unite state deliver stark warn north korean threat real u.s. air force general lori robinson previously head u.s. air force pacific tell lawmakers medium range try hard able hit homeland impossible know exactly much money expertise north koreans expend scale effort however see large many ways level commitment unite state give manhattan project build world first atomic bomb world war two pyongyang reason clear build kind credible ability strike see central long-term survival kim dynasty rule party early month first meet rule party 36 years kim say north korea responsible nuclear weapons state would never use weapons unless threaten seem clear warn outside power particularly washington steer clear attempt destabilize attack regime get submarine-based deterrent would big deal might allow north koreans move launch point much close target submarine central nuclear weapons state call second strike capability ability launch missiles even aftermath overwhelm perhaps surprise preemptive attack unite state russia britain france retain call continuous sea deterrent least one submarine offshore time ready fight back even homeland military force completely take israel also believe ability mount nuclear cruise missiles dolphin-class conventional submarine china move quickly towards new ballistic missile submarine sea deterrent technology new unite state russia develop late 1950s base part plan originally develop hit nazi german u-boats die days world war two good reason eventually work north korea pyongyang likely try keep submarine close coasts—and home defenses—at first still first nuclear-armed submarine exist japan unite state might feel political pressure destroy would come considerable risk north know huge volumes conventional artillery base along south korean border much range seoul 10 million residents risk weapons inflict massive casualties one key factor deter multiple u.s. administrations consider kind preemptive strike pyongyang weapons program unite state threaten iran korean war freeze 1953 cease-fire never otherwise resolve may yet commentary long north korea nuke u.s. city