Guadalcanal Campaign - Battle of Edson's Ridge

Battle of Edson's Ridge

On September 7, Kawaguchi issued his attack plan to "rout and annihilate the enemy in the vicinity of the Guadalcanal Island airfield." Kawaguchi's attack plan called for his forces, split into three divisions, to approach the Lunga perimeter inland, culminating with a surprise night attack. Oka's forces would attack the perimeter from the west while Ichiki's Second Echelon, now renamed the Kuma Battalion, would attack from the east. The main attack would be by Kawaguchi's "Center Body", numbering 3,000 men in three battalions, from the jungle south of the Lunga perimeter. By September 7, most of Kawaguchi's troops had departed Taivu to begin marching towards Lunga Point along the coastline. About 250 Japanese troops remained behind to guard the brigade's supply base at Taivu.

Meanwhile, native scouts under the direction of Martin Clemens, a coastwatcher officer in the Solomon Islands Protectorate Defense Force and the British district officer for Guadalcanal, brought reports to the U.S. Marines of Japanese troops at Taivu near the village of Tasimboko. Edson planned a raid on the Japanese troop concentration at Taivu. On September 8, after being dropped-off near Taivu by boat, Edson's men captured Tasimboko as the Japanese defenders retreated into the jungle. In Tasimboko, Edson's troops discovered Kawaguchi's main supply depot, including large stockpiles of food, ammunition, medical supplies, and a powerful shortwave radio. After destroying everything in sight, except for some documents and equipment carried back with them, the Marines returned to the Lunga perimeter. The mounds of supplies along with intelligence gathered from the captured documents informed the Marines that at least 3,000 Japanese troops were on the island and apparently planning an attack.

Edson, along with Colonel Gerald C. Thomas, Vandegrift's operations officer, correctly believed that the Japanese attack would come at a narrow, grassy, 1,000 yards (910 m)-long, coral ridge that ran parallel to the Lunga River located just south of Henderson Field. The ridge, called Lunga Ridge, offered a natural avenue of approach to the airfield, commanded the surrounding area and, at that time, was almost undefended. On September 11 the 840 men of Edson's battalion were deployed onto and around the ridge.

On the night of September 12 Kawaguchi's 1st Battalion attacked the Raiders between the Lunga River and ridge, forcing one Marine company to fall back to the ridge before the Japanese halted their attack for the night. The next night Kawaguchi faced Edson's 830 Raiders with 3,000 troops of his brigade plus an assortment of light artillery. The Japanese attack began just after nightfall with Kawaguchi's 1st battalion assaulting Edson's right flank just to the west of the ridge. After breaking through the Marine lines the battalion's assault was eventually stopped by Marine units guarding the northern part of the ridge.

Two companies from Kawaguchi's 2nd Battalion charged up the southern edge of the ridge and pushed Edson's troops back to Hill 123 on the center part of the ridge. Throughout the night Marines at this position supported by artillery defeated wave after wave of frontal Japanese attacks, some of which resulted in hand-to-hand fighting. Japanese units that infiltrated past the ridge to the edge of the airfield were also repulsed. Attacks by the Kuma battalion and Oka's unit at other locations on the Lunga perimeter were also defeated. On September 14 Kawaguchi led the survivors of his shattered brigade on a five day march west to the Matanikau Valley to join with Oka's unit. In total Kawaguchi's forces lost about 850 killed and the Marines 104.

On September 15 Hyakutake at Rabaul learned of Kawaguchi's defeat and forwarded the news to Imperial General Headquarters in Japan. In an emergency session the top Japanese IJA and IJN command staffs concluded that, "Guadalcanal might develop into the decisive battle of the war." The results of the battle now began to have a telling strategic impact on Japanese operations in other areas of the Pacific. Hyakutake realized that in order to send sufficient troops and materiel to defeat the Allied forces on Guadalcanal he could not at the same time support the major ongoing Japanese offensive on the Kokoda Track in New Guinea. Hyakutake, with the concurrence of General Headquarters, ordered his troops on New Guinea who were within 30 miles (48 km) of their objective of Port Moresby to withdraw until the "Guadalcanal matter" was resolved. Hyakutake prepared to send more troops to Guadalcanal for another attempt to recapture Henderson Field.