Guadalcanal Campaign - Actions Along The Matanikau

Actions Along The Matanikau

Vandegrift and his staff were aware that Kawaguchi's troops had retreated to the area west of the Matanikau and that numerous groups of Japanese stragglers were scattered throughout the area between the Lunga Perimeter and the Matanikau River. Vandegrift, therefore, decided to conduct another series of small unit operations around the Matanikau Valley. The purpose of these operations was to mop up the scattered groups of Japanese troops east of the Matanikau and to keep the main body of Japanese soldiers off-balance to prevent them from consolidating their positions so close to the main Marine defenses at Lunga Point.

The first U.S. Marine operation conducted between between September 23 and 27 by elements of three U.S. Marine battalions, an attack on Japanese forces west of the Matanikau, was repulsed by Kawaguchi's troops under Akinosuke Oka's local command. During the action three Marine companies were surrounded by Japanese forces near Point Cruz west of the Matanikau, took heavy losses, and barely escaped with assistance from the destroyer USS Monssen (DD-436) and landing craft manned by U.S. Coast Guard personnel.

In the second action between October 6 and 9 a larger force of Marines successfully crossed the Matanikau River, attacked newly landed Japanese forces from the 2nd Infantry Division under the command of generals Masao Maruyama and Yumio Nasu, and inflicted heavy losses on the Japanese 4th Infantry Regiment. The second action forced the Japanese to retreat from their positions east of the Matanikau and hindered Japanese preparations for their planned major offensive on the U.S. Lunga defenses.

Between October 9 and 11 the U.S. 1st Battalion 2nd Marines raided two small Japanese outposts about 30 miles (48 km) east of the Lunga perimeter at Gurabusu and Koilotumaria near Aola Bay. The raids killed 35 Japanese at a cost of 17 Marines and three U.S. Navy personnel killed.