▁chose ▁to ▁complete ▁their ▁system ▁around ▁Moscow ▁while ▁the ▁US ▁continued ▁with ▁construction ▁of ▁one ▁of ▁the ▁Saf egu ard ▁sites ▁outside ▁Grand ▁F ork s , ▁North ▁Dak ota . ▁The ▁argument ▁for ▁and ▁against ▁the ▁Saf egu ard ▁system ▁continued ▁both ▁in ▁the ▁military ▁and ▁public ▁aren as , ▁and ▁the ▁system ▁was ▁ultimately ▁shut ▁down ▁in ▁ 1 9 7 5 ▁after ▁only ▁one ▁day ▁of ▁official ▁operation . ▁ ▁Lo AD S ▁ ▁Cont inu ing ▁work ▁ ▁As ▁a ▁h edge ▁against ▁the ▁possibility ▁of ▁the ▁S ovi ets ▁" bre aking ▁out " ▁of ▁the ▁AB M ▁treat y , ▁the ▁Army ▁was ▁given ▁the ▁go - a head ▁to ▁continue ▁development ▁of ▁AB M ▁techn ologies , ▁foc using ▁on ▁the ▁Saf egu ard - like ▁concept ▁of ▁def ending ▁the ▁miss ile ▁fields . ▁The ▁Army ▁respond ed ▁with ▁two ▁concepts , ▁updates ▁to ▁the ▁original ▁Saf egu ard ▁using ▁a ▁new ▁rad ar ▁and ▁upgrad ed ▁S print ▁II ▁miss ile , ▁and ▁a ▁new ▁concept ▁for ▁a ▁high - alt itude ▁inter ceptor ▁that ▁would ▁use ▁hit - to - kill ▁instead ▁of ▁a ▁nuclear ▁war head . ▁Work ▁on ▁the ▁former , ▁known ▁as ▁Site ▁Def ence ▁of ▁Min ut eman , ▁went ▁as ▁far ▁as ▁building ▁a ▁rad ar ▁at ▁the ▁Army ' s ▁testing ▁site ▁on ▁Me ck ▁Island ▁in ▁the ▁K w aj ale in ▁At oll , ▁but ▁work ▁on ▁this ▁program ▁ended ▁in ▁ 1 9 7