The Actions along the Matanikau—sometimes referred to as the Second and Third Battles of the Matanikau—were two separate but related engagements between the United States and Imperial Japanese naval and ground forces in the Pacific theater of World War II. The actions occurred around the Matanikau River on Guadalcanal Island in the southwestern Pacific during the Guadalcanal campaign. These particular engagements—the first taking place between 23 and 27 September, and the second between 6 and 9 October—were two of the largest and most significant of the Matanikau actions.
The Matanikau River area includes a peninsula called Point Cruz, the village of Kokumbona, and a series of ridges and ravines stretching inland from the coast. Japanese forces used the area to regroup from attacks against U.S. forces on the island. From there, they launched further attacks on the U.S. defenses that guarded Henderson Field at Lunga Point on Guadalcanal, as a base to defend against Allied attacks directed at Japanese troop and supply encampments on western Guadalcanal, and as a location for watching and reporting on Allied activity around Henderson Field.
In the first action, elements of three U.S. Marine battalions under the command of U.S. Marine Major General Alexander Vandegrift attacked Japanese troop concentrations at several points around the Matanikau River. The Marine attacks were intended to "mop-up" Japanese stragglers retreating towards the Matanikau from the recent Battle of Edson's Ridge, to disrupt Japanese attempts to use the Matanikau area as a base for attacks on the Marine Lunga defenses, and to destroy any Japanese forces in the area. The Japanese—under the overall command of Major General Kiyotake Kawaguchi—repulsed the Marine attacks. During the action, three U.S. Marine companies were surrounded by Japanese forces, took heavy losses, and barely escaped with assistance from a U.S. Navy destroyer and landing craft manned by U.S. Coast Guard personnel.
In the second action two weeks later, a larger force of U.S. Marines successfully crossed the Matanikau River, attacked Japanese forces under the command of newly arrived generals Masao Maruyama and Yumio Nasu, and inflicted heavy casualties on a Japanese 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 set for later in October 1942 that resulted in the Battle for Henderson Field.
Background
On 7 August 1942, Allied forces (primarily American) landed on Guadalcanal, Tulagi, and Florida Islands in the Solomon Islands, northeast of Australia. The landings on the islands were meant to deny their use by the Japanese as bases for threatening the supply routes between the U.S. and Australia, and secure the islands as starting points for a campaign with the eventual goal of neutralizing the major Japanese base at Rabaul while also supporting the Allied New Guinea campaign. The landings initiated the six-month-long Guadalcanal Campaign. Taking the Japanese by surprise, by nightfall on 8 August the Allied landing forces had secured Tulagi and nearby small islands, as well as an airfield, later called Henderson Field by Allied forces, under construction at Lunga Point on Guadalcanal.
In response to the Allied landings on Guadalcanal, the Japanese Imperial General Headquarters assigned the Imperial Japanese Army's 17th Army—a corps-sized command based at Rabaul and under the command of Lieutenant-General Harukichi Hyakutake—with the task of retaking Guadalcanal from Allied forces. The 17th Army, by this time heavily involved with the Japanese campaign in New Guinea, had only a few units available to send to the southern Solomons area. Of these units, the 35th Infantry Brigade under Major General Kiyotake Kawaguchi was at Palau, the 4th (Aoba) Infantry Regiment under Major General Yumio Nasu was in the Philippines and the 28th (Ichiki) Infantry Regiment was embarked on transport ships near Guam. The different units began to move towards Guadalcanal immediately, but Ichiki's regiment—being the closest—arrived first. The "First Element" of Ichiki's unit—consisting of about 917 soldiers—landed from destroyers at Taivu Point, east of the Lunga perimeter, on 19 August, attacked the U.S. Marine defenses, and were almost completely annihilated during the resulting Battle of the Tenaru on 21 August.
Between 29 August and 7 September, Japanese destroyers (called "Tokyo Express" by Allied forces), plus a convoy of slow barges, delivered the 6,000 men of Kawaguchi's brigade, including the rest of Ichiki's regiment (called the Kuma Battalion) and much of the Aoba regiment, to Guadalcanal. General Kawaguchi and 5,000 of the troops landed 20 mi (32 km) east of the Lunga Perimeter at Taivu Point. The other 1,000 troops—under the command of Colonel Akinosuke Oka—landed west of the Lunga Perimeter at Kokumbona. During this time, Vandegrift continued to direct efforts to strengthen and improve the defenses of the Lunga perimeter. Between 21 August and 3 September, he relocated three Marine battalions—including the 1st Raider Battalion, under U.S. Lieutenant Colonel Merritt A. Edson (Edson's Raiders)—from Tulagi and Gavutu to Guadalcanal.
Kawaguchi's Center Body of 3,000 troops began their attacks on a ridge south of Henderson Field beginning on 12 September in what was later called the Battle of Edson's Ridge. After numerous frontal assaults, Kawaguchi's attack was repulsed with heavy losses for the Japanese, who retreated into the jungle on 14 September. Oka's assault in the west and the Kuma Battalion's assault in the east were also repulsed by the U.S. Marines over the same two days. Kawaguchi's units were ordered to withdraw west to the Matanikau Valley to join with Oka's unit on the west side of the Lunga Perimeter. Most of Kawaguchi's men reached the Matanikau by 20 September.
As the Japanese regrouped west of the Matanikau, the U.S. forces concentrated on shoring up and strengthening their Lunga defenses. On 18 September, an Allied naval convoy delivered 4,157 men from the 3rd Provisional Marine Brigade (U.S. 7th Marine Regiment) to Guadalcanal. These reinforcements allowed Vandegrift—beginning on 19 September—to establish an unbroken line of defense completely around the Lunga perimeter.
The Japanese immediately began to prepare for their next attempt to recapture Henderson Field. The 3rd Battalion, 4th (Aoba) Infantry Regiment had landed at Kamimbo Bay on the western end of Guadalcanal on 11 September, too late to join Kawaguchi's attack on the U.S. Marines. By then, though, the battalion had joined Oka's forces near the Matanikau. Subsequent Tokyo Express runs—beginning on 15 September—brought food and ammunition—as well as 280 men from the 1st Battalion, Aoba Regiment—to Kamimbo on Guadalcanal.
U.S. Marine Lieutenant General 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. Two previous raids by Marines—on 19 and 29 August—had killed some of the Japanese forces camped in that area but had failed to deny the location as an assembly area and defensive position for the Japanese forces threatening the western portion of the Marine defenses. 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 operation was assigned to the 1st Battalion, 7th Marine Regiment under Lieutenant Colonel Lewis Burwell "Chesty" Puller with a start date of 23 September. The operation would be supported by artillery fire from the U.S. 11th Marine Regiment.
September action
Prelude
The U.S. Marine plan called for Puller's battalion to march west from the Lunga perimeter, scale a large terrain feature called Mount Austen, cross the Matanikau River, and then reconnoiter the area between the Matanikau and Kokumbona village. At the same time, the 1st Raider Battalion—now under the command of Lieutenant Colonel Samuel B. Griffith—was to cross at the mouth of the Matanikau to explore the area between the river, Kokumbona, and further west towards Tassafaronga. The Marines thought that there were about 400 Japanese in that area.
The actual number of Japanese troops in the Matanikau Valley was much higher than the Marine estimate. Believing that the Allies might attempt a major amphibious landing near the Matanikau River, Kawaguchi assigned Oka's 124th Infantry Regiment—numbering about 1,900 men—to defend the Matanikau. Oka deployed his "Maizuru" Battalion around the base of Mount Austen and along the west and east banks of the Matanikau River. The rest of Oka's force was located west of the Matanikau, but in position to respond quickly to any Allied attacks in that area. Including other Japanese troops located near Kokumbona, total Japanese forces in the general Matanikau area numbered about 4,000.
Action
The 930 men of Puller's battalion marched west from the Lunga perimeter early on the morning of 23 September. Later that morning, Puller's troops chased away two Japanese patrols that were reconnoitering the Marine Lunga defenses. Puller's battalion then camped for the night and prepared to climb Mount Austen the next day.
At 17:00 on 24 September, as Puller's men hiked up the northeast slope of Mount Austen, they surprised and killed a bivouac of 16 Japanese soldiers. The noise from the skirmish alerted several companies of Oka's Maizuru Battalion, who were emplaced nearby. The Maizuru troops quickly attacked Puller's Marines, who took cover and returned fire. Acting on Oka's orders, the Japanese slowly disengaged while withdrawing towards the Matanikau River, and the engagement was over by nightfall. The Marines counted 30 dead Japanese and had suffered 13 dead and 25 wounded. Puller radioed headquarters and requested help to evacuate the wounded. Vandegrift replied that he would send the 2nd Battalion, 5th Marine Regiment (2/5) as reinforcements the next day.
2/5—under Lieutenant Colonel David McDougal—rendezvoused with Puller's unit early on 25 September. Puller sent his casualties back to the Lunga perimeter with three companies of his battalion and continued on with the mission with his remaining company (Company C), his headquarters staff, and 2/5, and they bivouacked for the night between Mount Austen and the Matanikau River.
On the morning of 26 September, Puller and McDougal's troops reached the Matanikau River and attempted to cross over a bridge previously built by the Japanese that was called the "one-log bridge". Because of resistance by about 100 Japanese defenders around the bridge, the Marines instead proceeded north along the east bank of the Matanikau to the sand spit on the coast at the mouth of the river. Oka's troops repulsed a Marine attempt to cross the Matanikau at the sand spit as well as another attempt to cross the one-log bridge later in the afternoon. In the meantime, Griffith's Raider battalion—along with Merritt A. Edson, commander of the 5th Marine Regiment—joined Puller and McDougal's troops at the mouth of the Matanikau.
Edson brought with him a "hastily devised" plan of attack—primarily written by Lieutenant Colonel Merrill B. Twining, a member of Vandegrift's division staff—that called for Griffith's Raiders—along with Puller's Company C—to cross the one-log bridge and then outflank the Japanese at the river mouth/sand spit from the south. At the same time, McDougal's battalion was to attack across the sand spit. If the attacks were successful, the rest of Puller's battalion would land by boat west of Point Cruz to take the Japanese by surprise from the rear. Aircraft from Henderson Field—as well as Marine 75 mm (2.95 in) and 105 mm (4.1 in) artillery—would provide support for the operation. The Marine offensive would begin the next day, on 27 September.
The Marine attack on the morning of 27 September did not make much headway. Griffith's Raiders were unable to advance at the one-log bridge over the Matanikau, suffering several casualties, including the death of Major Kenneth D. Bailey and the wounding of Griffith. A flanking attempt by the Raiders further upstream also failed. The Japanese, who had reinforced their units at the mouth of the Matanikau during the night with additional companies from the 124th Infantry Regiment, repulsed the attacks by McDougal's men.
As a result of "garbled" messages from Griffith because of a Japanese air raid on Henderson Field that disrupted the Marine communications net, Vandegrift and Edson believed that the Raiders had succeeded in crossing the Matanikau. Therefore, Puller's battalion was ordered to proceed with the planned landing west of Point Cruz. Three companies of Puller's battalion, under Major Otho Rogers, landed from nine landing craft just west of Point Cruz at 13:00. Rogers' Marines pushed inland and occupied a ridge, called Hill 84, about 600 yd (550 m) from the landing area. Oka—recognizing the seriousness of this landing—ordered his forces to close on Rogers' Marines from both the west and east.
Soon after occupying the ridge, Rogers' men came under heavy fire from two directions from Oka's forces. Major Rogers was hit by a mortar shell and died instantly. Captain Charles Kelley—commander of one of the companies—took command and deployed the Marines in a perimeter defense around the ridge to fight back. The Marines on Hill 84 were without radio communication and thus could not call for help. The Marines improvised by using white undershirts to spell out the word "H-E-L-P" on the ridge. A Cactus Air Force (the name for the Allied aircraft operating out of Henderson Field) SBD Dauntless supporting the operation spotted the undershirt message and relayed the message to Edson by radio.
Paul Moore Jr., a Marine veteran who participated in the battle, described it: