On September 4 , Haynes changed the boundary between the 38th and 23rd Infantry Regiments , giving the northern part of the 23rd 's sector to the 38th Infantry , thus releasing 1st Battalion for movement southward to help the 2nd Battalion defend the southern approach to Changnyong . The 1st Battalion , 23rd Infantry , about 1 @,@ 100 men strong when the attack began , was now down to a strength of approximately 600 men . The 23rd Infantry now made plans to concentrate all its troops on the position held by its 2nd Battalion on the Pugong @-@ ni @-@ Changnyong road . The 1st Battalion moved there and took a place on the left flank of the 2nd Battalion . At the same time the regimental command post moved to the rear of this position . In this regimental perimeter , the 23rd Infantry fought a series of hard battles . Simultaneously it had to send combat patrols to its rear to clear infiltrating North Koreans from Changnyong and from its supply road .