The third battle of the Matanikau

On 7 October 1942 the US Marines on Guadalcanal launched their third attack in two months along the Matanikau River, which closed off the area around Henderson Field to the west. This time, unlike in September, the operation was carefully planned, directed by the division staff itself and supported by artillery and aircraft. For three days five Marine battalions drove back and surrounded the Japanese on both banks of the river. The blow struck the enemy just as he was preparing an attack of his own: the Japanese 4th Infantry Regiment lost about 700 killed, the Americans 65. The Japanese lost the positions from which they had intended to launch their great October offensive and had to change its plan completely.

A river fought over since August

The Matanikau flows from the mountains of the interior to the north coast, a few kilometres west of the American defensive perimeter around Lunga Point. Its mouth, the sandspit along the shore and the nearby promontory of Point Cruz had been the scene of patrol clashes from the first weeks of the campaign. In August the Marines ventured west of the river several times, and on 23–27 September they made an unsuccessful attack there: companies of Lieutenant Colonel Lewis “Chesty” Puller’s 1st Battalion, 7th Marines, landed west of Point Cruz, were surrounded and had to be taken off by boat under the cover of a destroyer – and Coast Guard Signalman Douglas Munro was killed covering the withdrawal. The September defeat was a painful lesson for the commanders of the 1st Marine Division: the attack had been mounted in haste, without reconnaissance, with divided forces and unreliable communications.

Meanwhile, after the defeat of General Kiyotake Kawaguchi’s troops at Bloody Ridge in mid-September, the headquarters of the Japanese 17th Army at Rabaul decided to throw much larger forces onto Guadalcanal. Between 1 and 5 October night convoys of destroyers – which the Americans called the Tokyo Express – brought to the island units of the 2nd (Sendai) Infantry Division together with its commander, Lieutenant General Masao Maruyama. Major General Yumio Nasu deployed three battalions of Colonel Tadamasu Nakaguma’s 4th Infantry Regiment on the west bank of the Matanikau, south of Point Cruz, and moved three companies across to the east bank. They were to seize a bridgehead and positions from which heavy artillery could shell the airfield and the whole Lunga perimeter. The exhausted troops of Colonel Akinosuke Oka, who had held the sector in September, were withdrawn.

The Americans observed these movements from the air and through patrols and reports from Australian coastwatchers. The commander of the 1st Marine Division, Major General Alexander Vandegrift, decided that he could not allow the Japanese to dig in along the river. His perimeter was growing stronger – the Seabees were extending and repairing the airfield, and the South Pacific command had at last agreed to send a US Army infantry regiment to the island – but intelligence predicted another Japanese attack soon.

A plan that had learned its lessons

The plan for the October operation resembled the September one but was more careful in every respect. Five battalions took part. Two battalions of the 5th Marines, commanded since 21 September by Colonel Merritt Edson – the victor of Bloody Ridge – were to advance along the coast to the mouth of the Matanikau, pin down the Japanese on the east bank and feint a crossing at the sandspit. Meanwhile the main body was to cross the river inland, at a makeshift footbridge known as the “one-log bridge”, and then wheel north towards the sea. It consisted of two battalions of Colonel Amor LeRoy Sims’s 7th Marines – Puller’s 1st Battalion and Lieutenant Colonel Herman Hanneken’s 2nd Battalion – and the so-called Whaling Group: the 3rd Battalion, 2nd Marines, reinforced with the division’s scouts and snipers under Colonel William J. Whaling. The enveloping columns were to pin the Japanese against the coast between the Matanikau and Point Cruz.

This time the division staff kept control of the operation as a whole. Support from the artillery of the 11th Marines and from aircraft at Henderson Field was carefully scheduled, and the 3rd Battalion, 1st Marines, with a group of boats, was held in reserve, ready to move off within half an hour. The attack across the river was set for 8 October; on 7 October the units were to leave the perimeter and take up their starting positions.

The Americans did not yet know that the Japanese were preparing an almost mirror-image attack. Documents later found on a dead Japanese officer showed that the 17th Army had itself intended to cross the Matanikau near the fork of the river while attacking at its mouth, in order to move artillery into positions from which it could shell the airfield. According to the 1949 Marine Corps monograph, the date of this Japanese attack fell on the very day that Vandegrift had set for his battalions.

7 and 8 October: the pocket at the river mouth

On the morning of 7 October Edson’s battalions moved west along the coast. Before noon the leading 3rd Battalion, 5th Marines, ran into a Japanese force of roughly company strength in the strip of coastal jungle – the 3rd Company of the 1st Battalion, 4th Infantry Regiment. The Japanese fell back slowly into a prepared bridgehead on the east bank, a few dozen metres from the mouth: a network of trenches, machine-gun positions and foxholes. Some of them managed to cross the sandspit to the far bank, but between about 150 and 200 men, according to various accounts, remained in the bridgehead. The Marines surrounded them on three sides, supported by the fire of 75 mm guns on half-tracks (M3 GMC); the Japanese 2nd Company, which tried to come to the aid of the trapped men from the west bank, failed to force the river and suffered losses. Edson asked for reinforcements, and Vandegrift sent him, one after another, companies of the 1st Marine Raider Battalion, which had defended Bloody Ridge a month earlier.

At the same time the Whaling Group and the battalions of the 7th Marines reached the vicinity of the inland footbridge unopposed and bivouacked there. General Nasu, unaware of the American operation, moved yet another company – the 9th Company of the 3rd Battalion of his regiment – to the east bank on the evening of 7 October. Only at about 3 a.m. did the Japanese regimental commander receive word of the Marine attack, and he moved his 1st and 2nd Battalions closer to the river.

On 8 October torrential rain broke over the island. Steep, clay slopes and swollen streams meant that the attack across the river had to be postponed by a day. Vandegrift agreed reluctantly, knowing that he was losing some of the element of surprise. Part of the force crossed the river nevertheless: in the evening the 3rd Battalion, 2nd Marines, took the first ridge on the west bank, about one and a half kilometres from Point Cruz, while Company H of Hanneken’s battalion, on the east side, blundered in between the Japanese 9th Company and the rest of its battalion on the far side of the river and had to pull back. The Japanese commanders, Maruyama and Nasu included, still did not grasp the danger and ordered their units to hold their positions.

On the evening of 8 October the Japanese trapped in the bridgehead at the river mouth made a last, determined attempt to break out across the sandspit. They struck where it was least expected – at the positions of two platoons of Raiders who had relieved an exhausted company of the 5th Marines that morning. In the darkness, amid smoke and mist, a fierce hand-to-hand fight ensued. Twelve Raiders were killed (22 were wounded), as were 59 Japanese, whose bodies were counted the next day; some of the trapped men nevertheless got across to the other bank and reached their own lines.

9 October: “a machine of extermination”

Meanwhile on 8 October aircraft, coastwatchers and radio intercepts brought news that worried Vandegrift: ships were gathering at Rabaul, and everything pointed to a heavy Japanese blow in the near future, possibly combined with a landing near the perimeter. The original plan had envisaged that after a successful attack the Marines would push on westwards through Kokumbona and leave a permanent garrison there. Now the general decided that he could not weaken the airfield’s defences for so long. He resolved that the attack would go ahead as planned, but that once the Japanese along the Matanikau had been crushed, all units would return to the east bank.

On the morning of 9 October the Whaling Group, advancing towards the sea with its right flank along the river, took the whole west bank down to the mouth. To its left Hanneken’s battalion passed through Matanikau village and reached the base of Point Cruz, cutting off the Japanese line of retreat; the men of the 4th Regiment trapped between it and the river died under artillery fire and air attack. The bloodiest episode took place still further west, in the sector of Puller’s battalion. When his Marines reached the last ridges above the coastal plain, they saw a large concentration of Japanese infantry in a wooded ravine in front of them – the 2nd Battalion, 4th Infantry Regiment. Puller had orders to reconnoitre the route towards Kokumbona and not to become involved in heavy fighting, but with Sims’s approval he called down the fire of three battalions of the 11th Marines on the ravine ahead and covered the gully to his left with the fire of all his mortars.

The Japanese, unable to gather for a counter-attack under the bombardment, tried to escape up the opposite slope. As they emerged from the undergrowth they ran into the fire of the Marines’ machine guns and rifles; the survivors went back into the ravine, from which the artillery drove them out again. Puller himself later called it “a machine of extermination”, and the Marine Corps monograph “scientific extermination”. The shelling went on until the mortar ammunition began to run out and the time came to withdraw. Puller was unable to estimate the enemy’s losses. Only a diary later found on an officer of the 4th Regiment spoke of the loss of 690 men in the clash with his battalion.

In accordance with Vandegrift’s decision, all the Marine units withdrew to the east bank of the Matanikau on 9 October. This time it was not a retreat under enemy pressure but a planned withdrawal after the task had been accomplished.

Losses

Estimates of Japanese losses are approximate and rest largely on body counts and captured documents. The diary of the 4th Regiment officer speaks of 690 men lost in the clash with Puller’s battalion (not necessarily all of them killed), and to these must be added those who fell in the pocket at the river mouth and near Point Cruz. Historians, among them Richard B. Frank, put the regiment’s total losses at about 700 killed; one of its battalions had in effect ceased to exist. The Marines lost 65 killed and, according to Frank, 125 wounded.

Place in the war

On the same night that the Marines were returning across the Matanikau, the commander of the 17th Army, Lieutenant General Harukichi Hyakutake, landed on Guadalcanal to lead the great October offensive in person. On arrival he learned of the loss of the positions on the east bank and the destruction of one of the battalions of the 4th Regiment. When he passed this news to Tokyo, Lieutenant General Moritake Tanabe of the Army General Staff noted in his diary that the loss of the Matanikau positions was “a very bad sign”.

The consequences proved greater than the scale of the engagement would suggest. The Japanese concluded that retaking the east bank would require too many troops, and changed the plan of their offensive. An attack along the coast at the mouth of the Matanikau, supported by tanks and artillery, was now to be only a diversion, while the main body of Maruyama’s 2nd Division was to circle round the American perimeter through the jungle and strike the airfield from the south. The march, begun on 16 October along a path hacked through the undergrowth and later known as the Maruyama Trail, exhausted the troops, wrecked coordination and delayed the attack by several days. In the battle for Henderson Field on 23–26 October both Japanese attacks – at the river mouth and from the south – were bloodily repulsed, and on the southern sector of the defences Puller’s battalion was in the fight once again.

In the days immediately after the Matanikau battle the weight of the fighting shifted to the sea and the air. On the night of 11–12 October Rear Admiral Norman Scott’s American cruisers defeated a Japanese force off Cape Esperance; on 13 October the US Army’s 164th Infantry Regiment – the first Army unit on Guadalcanal – reached the island; and on the night of 13–14 October the Japanese battleships Kongō and Haruna deluged Henderson Field with shells.

The third battle of the Matanikau was the Marines’ first truly successful offensive action on Guadalcanal. It proved that the 1st Marine Division, barely two weeks after its September defeat at the same spot, had learned to plan coordinated attacks involving several battalions, artillery and aircraft. Above all, though, it wrecked the Japanese plan to attack the airfield from the most favourable direction and forced the enemy to choose the route through the jungle that did much to seal his defeat in October. The Matanikau and Point Cruz area remained a battleground until the American offensive of January, after which the Japanese evacuated the island at the beginning of February 1943.