US Marines conducted an amphibious landing at Cape Torokina , on the western coast of the island , north of Empress Augusta Bay , in November 1943 . After an initial counter @-@ attack , the US Marines had been replaced by a garrison of US Army troops who began consolidating their position around Torokina , establishing a strong perimeter . In March 1944 , the Japanese launched a heavy counter @-@ attack , which was turned back with heavy casualties . After this , the situation on Bougainville became largely static , as the Japanese focused primarily on subsistence , and the US forces chose to adopt a mainly defensive posture focused on maintaining the perimeter around Torokina .