The American counteroffensive of September 3 – 5 west of Yongsan , according to prisoner statements , resulted in one of the bloodiest debacles of the war for a North Korean division . Even though remnants of the NK 9th Division , supported by the low strength NK 4th Division , still held Obong @-@ ni Ridge , Cloverleaf Hill , and the intervening ground back to the Naktong on September 6 , the division 's offensive strength had been spent at the end of the American counterattack . The NK 9th and 4th divisions were not able to resume the offensive .