 On August 20 , the North Korean commands distributed operations orders to their subordinate units . The North Koreans called for a simultaneous five @-@ <unk> attack against the UN lines . These attacks would overwhelm the UN defenders and allow the North Koreans to break through the lines in at least one place to force the UN forces back . Five battle groupings were ordered . The center attack called for the <unk> 9th Division , <unk> 4th Division , <unk> 2nd Division , and <unk> 10th Division break through the US 2nd Infantry Division at the <unk> <unk> to <unk> and <unk> . 
