On 17 September , Vandegrift sent two companies from the 1st Battalion , 1st Marine Regiment ( 1 / 1 ) to pursue the retreating Japanese . The Marines were ambushed by two Japanese companies acting as rear @-@ guards for the withdrawal , and one Marine platoon was pinned down as the rest of the Marines retreated . The Marine company commander requested permission to attempt to rescue his platoon but was denied by Vandegrift . By nightfall , the Japanese overran and nearly annihilated the platoon , killing 24 Marines with only a few wounded members of the platoon surviving . On 20 September , a patrol from Edson 's Raiders encountered stragglers from Kawaguchi 's retreating column and called in artillery fire that killed 19 of them .