During the morning of 1 September , Walker weighed the news coming in from his southern front , wavering in a decision as to which part of the front most needed his Pusan Perimeter reserves . Since midnight the NK I Corps had broken his Pusan Perimeter in two places @-@ the NK 2nd and 9th Divisions in the US 2nd Division sector , and the NK 7th Division and NK 6th Division in the US 25th Division sector , below the junction of the Nam and Naktong Rivers . In the US 2nd Division sector North Korean troops were at the edge of Yongsan , the gateway to the corridor leading 12 miles ( 19 km ) eastward to Miryang and the main Pusan @-@ Mukden railroad and highway .