Matanikau Offensive - Background - Battle For Henderson Field

Battle For Henderson Field

Further information: Battle for Henderson Field

Between October 1 and October 17, the Japanese delivered 15,000 troops to Guadalcanal, giving Hyakutake 20,000 total troops to employ for his planned offensive. Because of the loss of their positions on the east side of the Matanikau, the Japanese decided that an attack on the U.S. defenses along the coast would be prohibitively difficult. Therefore, Hyakutake decided that the main thrust of his planned attack would be from south of Henderson Field. His 2nd Division (augmented by troops from the 38th Infantry Division), under Lieutenant General Masao Maruyama and comprising 7,000 soldiers in three infantry regiments of three battalions each was ordered to march through the jungle and attack the American defences from the south near the east bank of the Lunga River. To distract the Americans from the planned attack from the south, Hyakutake's heavy artillery plus five battalions of infantry (about 2,900 men) from the 4th and 124th Infantry Regiments under the overall command of Major General Tadashi Sumiyoshi were to attack the American defenses from the west along the coastal corridor.

Sumiyoshi's forces, including two battalions of the 4th Infantry Regiment under Colonel Nomasu Nakaguma, launched attacks on the U.S. Marine defenses at the mouth of the Matanikau on the evening of October 23. U.S. Marine artillery, cannon, and small arms fire repulsed the assaults and killed many of the attacking Japanese soldiers while suffering only light casualties to themselves.

Beginning on October 24 and continuing over two consecutive nights, Maruyama's forces conducted numerous, unsuccessful frontal assaults on the southern portion of the U.S. Lunga perimeter. More than 1,500 of Maruyama's troops were killed in the attacks while the Americans lost about 60 killed.

Further Japanese attacks near the Matanikau on October 26 by Oka's 124th Infantry Regiment were also repulsed with heavy losses for the Japanese. Thus, at 08:00 on October 26, Hyakutake called off any further attacks and ordered his forces to retreat. About half of Maruyama's survivors were ordered to retreat back to the area west of the Matanikau River while the rest, the 230th Infantry Regiment under Colonel Toshinari Shoji, was told to head for Koli Point, east of the Lunga perimeter. The 4th Infantry Regiment retreated back to positions west of the Matanikau and around the Point Cruz area while the 124th Infantry Regiment took up positions on the slopes of Mount Austen in the upper Matanikau Valley.

In order to exploit the recent victory Vandegrift planned another offensive west of the Matanikau which would have two objectives: to drive the Japanese beyond artillery range of Henderson Field and to cut off the retreat of Maruyama's men towards the village of Kokumbona, location of the 17th Army's headquarters. For the offensive, Vandegrift committed the three battalions of the 5th Marine Regiment, commanded by Colonel Merritt Edson, plus the augmented 3d Battalion, 7th Marine Regiment (called the Whaling Group) commanded by Colonel William Whaling. Two battalions of the 2nd Marine Regiment would be in reserve. The offensive was supported by artillery from the 11th Marine Regiment and the 164th Infantry Regiment, CAF aircraft, and gunfire from U.S. Navy warships. Edson was placed in tactical command of the operation.

Defending the Matanikau area for the Japanese were the 4th and 124th Infantry Regiments. Nakaguma's 4th Infantry defended the Matanikau from the shore to about 1,000 yards (914 m) inland while Oka's 124th Infantry extended the line further inland along the river. Both regiments, which on paper consisted of six battalions, were severely understrength because of battle damage, tropical disease, and malnutrition. In fact, Oka described his command as at only "half strength."