 The First Battle of Maryang San ( 3 – 8 October 1951 ) , also known as the Defensive Battle of <unk> ( Chinese : <unk> ; pinyin : <unk> <unk> <unk> <unk> ) , was fought during the Korean War between United Nations ( UN ) forces — primarily Australian and British — and the Chinese communist People 's Volunteer Army . The fighting occurred during a limited UN offensive by US I Corps , codenamed Operation Commando . This offensive ultimately pushed the Chinese back from the Imjin River to the Jamestown Line and destroyed elements of four Chinese armies following heavy fighting . The much smaller battle at Maryang San took place over a five @-@ day period , and saw the 3rd Battalion , Royal Australian Regiment ( 3 RAR ) <unk> a numerically superior Chinese force from the tactically important Kowang @-@ San ( Hill 355 ) and Maryang San ( Hill 317 ) features , in conjunction with other units of the 1st Commonwealth Division . 
