minot air force base n.d. flat windy expanse south canadian border u.s. air force pilot fly bombers grandfathers fly use mid-20th century cable pulleys spring airmen airwomen must clear melt snow steel concrete doors silos house 150 nuclear-tipped ballistic missiles scatter across thousands square miles upper great plain u.s. nuclear arsenal patch weld re-skinned countless time build 25 62 years ago unite state find lock arm race rival superpower soviet union future issue campaign nov. presidential election democratic candidate hillary clinton say would call nuclear posture review last complete 2010 one first act upon take office republican candidate donald trump say would open reverse decades u.s. policy allow ally japan south korea acquire nuclear weapons deter strike north korea carry fifth large nuclear test month monday first visit minot air force base north dakota u.s. secretary defense ash carter say america nuclear deterrence bedrock security pentagon priority replace systems quite simply age even become unsafe unreliable ineffective carter say speak lectern front b-52 bomber load cruise missiles fact nuclear weapon delivery systems already extend decades beyond original expect service live choice replace platforms keep really choice replace lose carter say russia say build new nuclear weapons systems raise question whether leaders cautious enough come atomic weapons north korea present sustain threat carter say carter speech coincide grow realization among defense officials experts budget constraints almost certainly force next president decide whether quickly proceed obama administration plan maintain modernize u.s. nuclear arsenal crunch come next decade american ballistic missile submarine bombers land-based missiles three legs nuclear triad reach end useful live congressional budget office estimate total cost nuclear force 2024 348 billion include costly upgrade schedule latter half next decade independent estimate put cost maintain modernize arsenal trillion dollars 30 years bipartisan commitment upgrade assume fund come energy secretary ernest moniz tell reuters sept. 20 significant budget increase especially next decade energy department share responsibility pentagon nuclear arsenal research production facilities 73 years old next administration could abandon delay aspects modernization cut cost could raise tax increase budget deficit cut domestic program unpopular step american voters vulnerable elements modernization plan long-range standoff weapon lrso nuclear-capable cruise missile launch aircraft new land-based intercontinental ballistic missiles icbms ten u.s. senators include elizabeth warren massachusetts bernie sanders vermont call president barack obama july cancel lrso say would provide unnecessary capability could increase risk nuclear war pentagon officials defense experts say cruise missile would hedge improve air defenses difficult even stealthy bomber penetrate clinton trump administration also could cut number land-based ballistic missiles 400 currently plan delay new missile extend life current minuteman iiis carry warhead explosive yield least 300 kilotons 20 time powerful atomic bomb drop hiroshima kill estimate 140,000 people unite state one five nuclear weapons state allow keep nuclear arsenal nuclear non-proliferation treaty others russia britain france china u.s. air force estimate cost new ground-based system include missiles command-and-control systems launch control center 60 billion former u.s. officials include former defense secretary william perry argue land-based missiles essential phase proponents say important face potential nuclear threats russia north korea much plan modernization nearly lock need new weapons far along say evan montgomery senior fellow center strategic budgetary assessments washington-based research group b-21 long-range strike bomber replacement navy 14 ohio-class ballistic missile submarine two expensive items arguably two safe lot ways montgomery say bomber deliver conventional nuclear weapons submarine consider priority would survive first strike adversary navy plan replace ohio-class submarine first commission 1981 arm 24 trident missiles multiple independently target warheads 12 boat cost 100 billion speech monday carter say people realize spend nuclear program small percentage total defense spend peak nuclear spend would make five percent pentagon budget around 600 billion annually defense experts say still fund gap mean despite pentagon massive budget next president face unavoidable dilemma doubt mind tens billions dollars short time frame take execute global strategy say jam miller former undersecretary defense policy obama administration round error anymore cost modernize u.s. nuclear weapons fall next president