The Battle of the Tenaru

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matthew hainer
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The Battle of the Tenaru

Post by matthew hainer » 21 Apr 2011 05:54

Hello, I will stick to the name " Battle of the Tenaru " to avoid confusion, even though the Battle took place on the Ilu river. However, when refering to river names, I will use the correct names. It is worth noting that the Marines refered to the Ilu river ( what the marines thought was the tenaru river ) as " Alligator creek "

In reading many sources of the Battle of the Tenaru, there are always a few minor details that are always in disagreement. So I will attempt to give the most clear, and most likely course of events that took place during the Battle of Tenaru.

A backround of events

On August 7th, 1942, United States Military forces commenced the Invasion of Guadalcanal. The Japanese forces on the Island, that of the 11th, 13th construction units, and a detachment of the Kure 3rd SNLF withdrew into the Jungle. The commanding officer of the 13th construction units, Captain Monzen believed it to be a raid, so he withdrew into the Jungle, but many other of the untrained construction workers ( as many as 1,000 ) simply fled into the Jungle because of the bombardment, and many starved to death. Vice Admiral Gunichi Mikawa, having recieved a flood of messages from the commander of Tulagi Island, immidiatly sent a strike force of G4M2, A6M2, D3A2 to counterattack the U.S invasion force. Due to clouds, the G4M2's all missed their targets while the Zero's dogfighted with American Wildcats sent up as interception. The D3A2 caused minor damage to a destroyer, however 5 of them were shot down by American Wildcats, while the remainder had to ditch since they did not have enough Fuel to return to Rebaul. Also on that day, Mikawa immidiatly scraped up 519 sailors, armed them with Machineguns and sent them as reinforcements to Guadalcanal on transports Meiyo Maru and Soya, screened by the minelayer Tsugaru and two small escorts. On August 8th, Mikawa left with his Counterattacking force of his flagship Chokai, Cruiser Division 6 of the Aoba, Furutaka, Kako, and Kinugasa. Also, Cruiser Division 18 with the Tenryu, Yubari joined him, along with the destroyer Yunagi. While this force set out, another air strike was sent towards Guadalcanal. 29 G4M2's took off, however only 6 made it back to Rebaul. Wildcats shot down 3 of them, while AA fire shot down the other G4M2's who were making their torpedo runs. For this large loss, only the destroyer Jarvis was hit by a Torpedo which caused some major damage, it later sank partially due to this damage, and one G4M2 crashed itself into the transport George E. Elliot which was later scuttled. 2 A6M2's were lost in this attack. When the scale of the Invasion became clear to Mikawa, he ordered the small convoy with the 519 sailors to turn back to Rebaul. On their way home, the Submarine S-38 sank the Meiyo Maru, and she took 373 men down with her. On the night of August 8th-9th Mikawa succesfully attacked U.S escorts for the Transports in the Battle of Savo Island, Where a large number of U.S cruisers and destroyers were either sunk or damaged, for little damage to Mikawa's forces. Because Mikawa being disorganized, and his fear of the U.S carrier planes ( which were out of range at this time, Mikawa did not know this ) Mikawa withdrew back to Rebaul. The Kako was sunk by a Submarine on its way back though. The Japanese began realizing how serrious the situation was at Guadalcanal, and planned to reinforce it with the 35 Brigade, Aoba detachment, and Ichiki detachment. The 35th Brigade was at Palau, the Aoba detachment was in the Philippines, but at the time the Ichiki detachment was departing from Guam. Since the Ichiki detachment was closest, it was to arrive first on Guadalcanal. Meanwhile, on August 12th, the Goettge patrol was wiped out by a platoon of the Kure 3rd SNLF. On August 16th, the destroyer Oite delivered 113 men of the Takahashi company, Yokosuka 5th SNLF at Tassafaronga Point. On August 19th, the first battle of the Matanakau was taking place, where the U.S killed 65 naval personel, probably of the Kure 3rd SNLF and armed Construction workers.

The Plan

The Ichiki detachment arrived at Truk, where his forces were split up. The 28th Regimental HQ would accompany the 2nd Battalion in what would make up the " First Echelon ". The First Echelon was to be transported by Destroyers Kagero, Hagikaze, Arashi, Tanikaze, Hamakaze, and Urakaze. A force of 250 SNLF was planned to be landed at Kokumbona as both a diversion and to support the eventual attack ( It is unknown to me as to whether this force of SNLF ever landed. Franks Guadalcanal book says " As a diversion, a detachment of about 250 Special Naval Landing Force troops would be placed ashore at Kokumbona, ... " (pg.145) also this link states 500 Yokosuka SNLF landed at Kokumbona. From what I have been researching, there is little to support these claims, but nonetheless I leave the information out here ). The Second Echelon would procede with the remainder of the Ichiki detachment on slow transports, with 500 Yokosuka 5th SNLF on the Kinryu Maru.

On August 19th, Ichiki and his First Echelon landed at Taivu point, where about 200 Naval personel stationed there helped with the offloading of supplies and men. Ichiki's First Echelon consisted of:
Detachment HQ : 164 Men
Battalion HQ ( 2nd Battalion, 28th Infantry ): 23 men
1st Company : 105 men
2nd Company: 105 men
3rd Company: 105 men
4th Company: 105 men
Machinegun Company ( 8 Heavy Machineguns ): 110 men
Battalion Gun Platoon ( two 7.0 cm type 92 guns ) : 50 men
Engineer Company ( 1st company, 7th engineer construction Regiment ): 150 men
Total: 917 men

Prior to the battle

Ichiki was supposed to wait at Taivu Point for the Second Echelon to arrive, and possibly more reinforcements, however feeling confident of victory, he marched off to Henderson Field. Captain Shibuya was sent ahead with the Regimental Signal section of about 38 men, to set up a communications point near Tetere. While laying Telephone wire, Shibuya's men made contact with the Brush patrol. The Japanese Hesitated for fear of the soldiers being fellow Japanese soldiers, while the Brush patrol set up positions to the flank of the patrol. Then Brush's men opened fire, and in a firefight lasting less than a hour, all but 5 of Shibuya's men were killed, those that survived fled back to Ichiki's HQ. The Americans, captured numerous Diarys and documents, as well as a detailed map of their positions along the Ilu river, which alarmed the Americans. Seeing the Star on corpses helmets, the Americans became aware that a sizable force of Army troops were landed recently, but they did not know the size, or its exact intentions. Ichiki immidiately sent a Company to bury the dead Japanese troops, and hurridly advanced his troops through the Jungles. He left behind around 100 men to help guard Taivu point. All of the 20th, he and his men advanced along the beach towards the American positions. At 1200 on August 20th, he gathered his Commanders and issued his attack plans. His troops were to march down the beach and attack as soon as U.S forces had been encountered. The objective was to take the old camp that used to belong to the 11th Construction Unit between the Ilu river and the Lunga. After that his units were to fan out and take the airfield and any positions occupied by the Americans. A patrol of Engineers would find suitable crossing points for the various rivers and streams, while the main colum followed closely behind. Ichiki was confident he could beat the American forces in a night attack, as he put it " with one brush of the armored sleeve."

The Battle

Marine listening poasts on the east bank of the Ilu river began hearing voices and clanking sounds, so they withdrew. At about midnight, a sentry on the Marine side of the Ilu river fired at a shape, which failed to reply back. The Marines began to sputter rifle fire across the river when noises were heard, probably created by Ichiki's Engineer patrol which would have been reaching the bank of the Ilu around midnight. The noise was probably the Engineers sumbling across a single strand of barbed wire that the Marines erected.The Japanese were suprised to have met Americans this far out, they had believed the Americans were closer to the Airfield. Ichiki who arrived at the Ilu river shortly after 0030, consulted with the Battalion Commander ( Major Kuramoto ) and his company commanders, and ordered them to assault the Marine positions at 0200. Throughout the time before the attack, the Japanese began getting into position. At 0200, The Japanese shot up a green flare which illuminated the entire area in a erie greenish glow. The Japanese line along the River erupted in Rifle and Machinegun fire. Almost in the instant, the 2nd Company began its charge acrossed the sand bar toward the Marine positions with shouts of Banzai and war crys. The Marines rifle and Machinegun fire from the front and side decimated the Japanese, and a 37mm gun positioned on the flank of the sand bar, opened up with canister shots, that exacted a heavy toll upon the Charging Japanese. Although, taking horrendous casualties, the troops of 2nd Battalion reached the other side but got held up by barbed wire. They either cut the wire or went over it, but despite taking continuous casualties the Japanese stormed over the wire and attacked Marine positions. With Gernades and Bayonets, the 2nd Company managed to take a few of the positions, and advanced a bit through the lines of the marines. However, in seeing a brakethrough, the Marine Battalion commander sent in a company to counterattack. The Japanese 2nd Company already decimated, could not hold its position, and was soon anhilated. During the 2nd company's attack, a bold LMG crew swam in the Ilu river onto a abandoned U.S amtrack and setup their LMG on it. Their Machinegun fire or grenades silenced the 37mm gun that had wreacked havoc on the charging 2nd Company along the sand bar. Japanese Covering fire managed to create some casualties among the Marines during the 2nd companies attack.

After the 2nd Company was destroyed in its failed attack, a second assault began a hour later. The 3rd Company Charged acrossed the sandbar, jumping over their dead comrades of the 2nd company, and they too were decimated. The Engineer Company also attacked at the same time acrossed the Ilu River alittle downstream. They too were decimated by Marine fire, and the few survivors retreated back to Japanese positions. A surviving officer from the 3rd Companys attack advised Ichiki to withdraw back to Taivu point, but for whatever reason, Ichiki refused. It may of been that he was unable to withdraw for some reason, or he had chosen to fight and die at his positions along the Ilu river. Whatever the reason, Ichiki's attacks had failed and he had lost hundreds of men already. He pulled back 200 yards into a cocunut grove and set up his HQ there. The Japanese who remained at the Ilu's edge continued to firefight with the Marines throughout the night, with Grenade Dischargers and the 7.0 cm guns firing at the Marines, Ichiki also threw in his MG company. The marines responded with their own rifle and machinegun fire, with adition to Mortar and 75 mm fire, which caused casualties and great confusion within Ichiki's lines. Apparently, it also broke up another group that appears to have been preparing for another charge acrossed the sand bar. At 0500, Ichiki sent his 1st Company through the surf of the Ocean in a attempt to outflank the Marine lines. They were spoted and raked with rifle and machinegun fire. Then mortars and 75mm guns joined in, and the company was decimated in the surf at the flank of the Marine lines, with the few survivors retreating back to the cocunut grove.

The destruction of the Ichiki's detachment

When the sun rose on August 21st, Colonel Ichiki had not withdrawn, he still remained in the Cocunut grove, with some of his men still shooting at marines along the Ilu river. While the Japanese were charging at the marine lines, the 1st battalion, 1st marines crossed the Ilu river downstream and proceded to flank the Japanese. Company C was the first to reach the coast on the Japanese side of the Ilu river, which completely surrounded the Japanese. A Japanese platoon counterattacked Company C in a Banzai styled charge, and the results are predictable. Company C was to be a blocking unit now, for any Japanese attempting to escape. Company's A and B began assaulting Ichiki's rear, and was met by resistance from remaining Japanese, but continued to advance, crompressing the Japanese. The Marines along the Ilu rivers edge picked off any Japanese who moved, while giving covering fire with their machineguns and mortars. Japanese began trying to retreat to the east, but they were mostly shot. A group that somehow got through A and B company ran into Company C where it was destroyed. American aircraft began strafing some Japanese who were attempting to swim back to Taivu point. At 1500 a platoon of 4 m3 stuarts rolled acrossed the sand bar, running over the piles of dead Japanese on the sand bar. The Japanese lacking any effective Anti-Tank weapons, began assaulting them with whatever weapons they had. They threw grenades or Magnetic anti-tank mines at them, while shooting them with rifles and machineguns. One of the Tanks was put out of action when a explosion broke one of its treads. The tanks just hunted down groups of surviving Japanese, and often ended up squashing them litteraly. By 1630, Ichiki burned the regemental flag, and committed suicide, just as a stuart discovered his small group( It is not known exactly what happened to Ichiki. According to a Captured soldier, Ichiki was last seen moving to the front lines, so its possible he was killed in one of the charges, this would explain why their was innaction by the Japanese who should have retreated during the night. Also, a marine claims to have killed Ichiki later on, when a wounded officer pulled out a pistol and shot at him ) Any remaining Japanese in the Cocunut grove were killed, and by 1700 all organized resistance ceased. Marine souvenire hunters began creeping by looking for items to send home. Wounded Japanese would sometimes take a grenade and blow themselves up near a Marine, or shoot at them. The Marines responded by Shooting at anything that twitched, and bayoneting much of the dead.


Ichiki's force was anhilated, only about 30 managed to make it back to Taivu point, to join the 100 that was left behind. One Japanese soldier surended, 12 wounded members were taken prisoner including one officer, and 2 unwounded survivors were captured as well. The Marines found that the Japanese Engineers had 8 flamethrowers, and the Japanese had alot of much needed entrenching tools. At no time was Henderson field ever in any serrious danger of being captured, the Japanese force was simply too small, and it had attacked without any real recconissance. The Second Echelon was turned back in the Battle of the Eastern Solomons, the Kinryu Maru was sunk with most of the 500 men of the Yokosuka 5th SNLF. The troops were sent to the Shortland Islands where they were eventually sent to Guadalcanal to join Kawaguchi's attack on Henderson Field. The remains of the Ichiki detachment and his Second Echelon were reorganized into the Kuma Battalion. In Comparison to later Battles the battle of the Tenaru was small, but it nonetheless just added to the amazing loss of life for the Japanese on Guadalcanal.

I wrote everything that I know about this battle. While some of the battle was hard to make out, since times vary, and no source could agree what units were sent in, and what time they were sent in. Nonetheless, I believe my outline of the battle is the most acruate, and I hope that anyone wishing for more knowledge on this would have been helped. If I have made any mistakes, or forgotten any information, please feel free to comment, I would love to learn more about the Battle of the Tenaru.

A map-

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