Expecting the Japanese to attack again that night , Edson directed his troops to improve their defenses on and around the ridge . After a failed attempt by two companies to retake the ground on the Marine right flank lost to Kokusho the night before , Edson repositioned his forces . He pulled his front back about 400 yd ( 370 m ) to a line that stretched 1 @,@ 800 yd ( 1 @,@ 600 m ) , starting at the Lunga River and crossing the ridge about 150 yd ( 140 m ) south of Hill 123 . Around and behind Hill 123 he placed five companies . Any Japanese attackers surmounting Hill 80 would have to advance over 400 yd ( 370 m ) of open terrain to close with the Marine positions at Hill 123 . With only a few hours to prepare , the Marines were only able to construct rudimentary and shallow fortifications . They were low on ammunition , with one or two grenades for each Marine . Vandegrift ordered a reserve force consisting of the 2nd Battalion , 5th Marine Regiment ( 2 / 5 ) to move into a position just to the rear of Edson 's troops . In addition , a battery of four 105mm howitzers from the 11th Marine Regiment moved to a location from where it could provide direct fire onto the ridge , and a forward artillery observer was placed with Edson 's front line units .