The Americans knew of the approach of the Japanese forces from reports from native scouts and their own patrols , but did not know exactly where or when they would attack . The ridge around which Edson deployed his men consisted of three distinct hillocks . At the southern tip and surrounded on three sides by thick jungle was Hill 80 ( so named because it rose 80 ft ( 24 m ) above sea level ) . Six hundred yards north was Hill 123 ( 123 ft ( 37 m ) high ) , the dominant feature on the ridge . The northernmost hillock was unnamed and about 60 ft ( 18 m ) high . Edson placed the five companies from the Raider battalion on the west side of the ridge and the three Parachute battalion companies on the east side , holding positions in depth from Hill 80 back to Hill 123 . Two of the five Raider companies , " B " and " C " , held a line between the ridge , a small , swampy lagoon , and the Lunga River . Machine @-@ gun teams from " E " Company , the heavy weapons company , were scattered throughout the defenses . Edson placed his command post on Hill 123 .