▁lines ▁and ▁attack ▁military ▁targets ▁and ▁cities . ▁ ▁UN ▁units , ▁spread ▁out ▁along ▁the ▁P us an ▁Per imeter , ▁had ▁a ▁difficult ▁time ▁rep elling ▁these ▁units ▁as ▁they ▁were ▁un tra ined ▁in ▁comb ating ▁gu err illa ▁war fare . ▁North ▁Korean ▁special ▁forces ▁units ▁like ▁the ▁NK ▁ 7 6 6 th ▁Independent ▁Infantry ▁Regiment ▁had ▁great ▁success ▁in ▁defe ating ▁R OK ▁troops , ▁prompt ing ▁U . S . ▁Army ▁Chief ▁of ▁Staff ▁General ▁J . ▁Law ton ▁Collins ▁to ▁order ▁the ▁creation ▁of ▁an ▁el ite ▁force ▁which ▁could ▁" in fil tr ate ▁through ▁enemy ▁lines ▁and ▁attack ▁command ▁posts , ▁art illery , ▁tank ▁par ks , ▁and ▁key ▁communic ations ▁cent ers ▁or ▁facilities ." ▁All ▁U . S . ▁Army ▁R anger ▁units , ▁which ▁had ▁previously ▁undert aken ▁this ▁role , ▁had ▁been ▁dis band ed ▁after ▁World ▁War ▁II ▁because ▁they ▁required ▁time - consum ing ▁training , ▁special ization , ▁and ▁expensive ▁equipment . ▁With ▁the ▁defeat ▁of ▁the ▁NK ▁ 7 6 6 th ▁Regiment ▁at ▁the ▁Battle ▁of ▁P ' oh ang - d ong , ▁and ▁the ▁strength ▁of ▁U . S . ▁inf antry ▁units ▁in ▁question , ▁U . S . ▁command ers ▁felt ▁the ▁recre ation ▁of ▁R anger ▁units ▁was ▁essential . ▁In ▁early ▁August ▁as ▁the ▁Battle ▁of ▁P us an ▁Per imeter ▁began , ▁the ▁E ighth ▁United ▁States ▁Army ▁ordered ▁Lieutenant ▁Colonel ▁John ▁H . ▁McG ee