Meanwhile , Kawaguchi 's 2nd Battalion , under Major Masao Tamura , assembled for their planned assault against Hill 80 from the jungle south of the ridge . Marine observers spotted Tamura 's preparations and called in artillery fire . At about 22 : 00 , a barrage from twelve 105 mm ( 4 @.@ 1 in ) guns hit Tamura 's position . In response , two companies of Tamura 's troops — numbering about 320 men — charged up Hill 80 with fixed bayonets behind their own barrage of mortar fire and grenades . Tamura 's attack hit Company B of the Marine Parachute battalion and also Raider Company B , pushing the Parachutists off the east side of the ridge into a draw below the ridgeline . To protect the exposed Raider Company B , Edson immediately ordered them to pull back onto Hill 123 .