Guadalcanal campaign

The Guadalcanal campaign, also known as the Battle of Guadalcanal and as Operation WATCHTOWER, was an American victory over Japan in 1942.

It was the first major Allied offensive of World War Two in the Pacific, and was fought between August 7, 1942 and February 9, 1943. This campaign pitted American air, naval and ground forces (later augmented by Australians and New Zealanders) against determined Japanese resistance. There were a succession of ground and naval battles.

Control of the Solomon Islands, of which Guadalcanal was a part, was considered militarily vital by both sides. Both sides won some battles but both sides were overextended and logistical failures in a hostile physical environment hampered the abilities of combat forces to operate. As happened time and again in the Pacific, the Japanese logistical support system failed. Only 20% of the supplies dispatched from Rabaul to Guadalcanal ever reached there. As a result the 30,000 Japanese troops lacked heavy equipment, adequate ammunition and even enough food, and were subjected to continuous harassment from the air. 10,000 were killed, 10,000 starved to death, and the remaining 10,000 were evacuated in February 1943, in a greatly weakened condition. In the end Guadalcanal was a major American victory as the Japanese inability to keep pace with the rate of American reinforcements proved decisive. Guadalcanal is an iconic episode in the annals of American military history, underscoring heroic bravery of underequipped individuals in fierce combat with a determined foe.

Summary

On August 7, 1942, United States Marines made amphibious landings on the islands of Guadalcanal, Tulagi, and Florida in the southern Solomons with the objective of denying their use by Japanese forces as bases to attack supply routes between the U.S. and Australia. The Allies further intended to use Guadalcanal and Tulagi as bases to support a campaign to eventually isolate the major Japanese base of Rabaul on the island of New Britain. The initial Allied landings overwhelmed the outnumbered and surprised Japanese defenders, who had occupied the islands in May, 1942, and captured an airfield that was under construction by the Japanese on Guadalcanal. Renamed Henderson Field after Major Lofton Henderson, a US Marine pilot killed at the Battle of Midway in June, the field was pressed into American service. U.S. Army forces later supplemented, and eventually relieved, the Marines.

The Japanese made several attempts to retake Tulagi and Henderson Field, resulting in three major land battles as well as several smaller engagements, five large naval battles, and continuous, almost daily, aerial battles, culminating in the decisive Naval Battle of Guadalcanal in early November 1942, in which the last Japanese attempt to retake Guadalcanal and Henderson Field was defeated.

The Guadalcanal campaign, lengthy by Pacific War standards, marked the first significant strategic combined arms victory by Allied forces over Japanese forces in the Pacific theater. For this reason, the Guadalcanal Campaign is often referred to as a "turning point" in the war. This campaign marked the beginning of the transition by Allied forces from defensive operations to the strategic offensive while the forces of Japan were thereafter forced to focus on strategic defense.

There were major command changes during the campaign, when Vice Admiral William Halsey replaced Vice Admiral Robert Ghormley as head of the South Pacific Area. Halsey brought greater Navy support of the land operations.

Strategy

Japanese strategy

On December 7, 1941, expanding its earlier war in China, the Empire of Japan attacked the the U.S. Pacific fleet in the attack on Pearl Harbor, as part of a broader series of attacks on Malaya, the Philippines, Singapore, the Dutch East Indies, and elsewhere against American, British, Dutch and Australian bases. The attack crippled much of the U.S. battleship fleet and led to a state of war between the two nations. In launching this war, Japanese leaders sought to neutralize the American fleet, seize possessions rich in natural resources, and obtain strategic military bases to defend their far-flung empire. While their major territorial goals were in Southeast Asia and Oceania, Admiral Isoroku Yamamoto, Commander-in-Chief, Combined Fleet, who opposed the overall war, was convinced the U.S. forces had to be neutralized to avoid intervention.

Two attempts by the Japanese to extend their defensive perimeter in the south and central Pacific were thwarted in the battles of Coral Sea (May 1942) and Midway (June 1942). These two strategic victories for the Allies provided an opportunity to take the initiative and launch an offensive against the Japanese somewhere in the Pacific. Admiral Ernest J. King, the US Chief of Naval Operations, chose the Solomon Islands, specifically the southern Solomon islands of Guadalcanal, Tulagi, and Florida.

American strategy

In the spring and summer of 1942, Admiral King, fought hard in meetings of the US Joint Chiefs of Staff for a limited offensive in the Pacific. He was opposed by General George C. Marshall, the Army's Chief of Staff, who believed strongly in a Germany-first policy and who did not want to divert any army or air force resources to support a Pacific offensive. Eventually, King threatened to go ahead on his own, using as his authority several ambiguous memoranda that had been approved earlier by President Franklin D. Roosevelt. Thus, on 7 August 1942, the US invasion of Guadalcanal took place, and this soon became a battle of attrition in which neither side would quit. Marshall never gave his full support to the operation, but it continued and the US forces were finally successful.

The specific plan to attack the southern Solomons was conceived by King's planners in Washington, who proposed the offensive to deny the use of the southern Solomon islands by the Japanese as bases to threaten the supply routes between the U.S. and Australia, and to use them as starting points for a campaign with the goal of isolating the major Japanese base at Rabaul while also supporting the Allied New Guinea campaign, with the eventual goal of opening the way for the U.S. to retake the Philippines. U.S. Admiral Chester Nimitz, Commander in Chief, United States Pacific Fleet and Pacific Ocean Areas, created the South Pacific theater, with U.S. Vice Admiral Robert L. Ghormley place in command on June 19, 1942, to direct the Allied offensive in the Solomons.

Allied strategists knew the Japanese Navy had occupied Tulagi in May 1942 and had constructed a seaplane base near there. Concern grew when in early July 1942 the Japanese Navy began constructing a large airfield near Lunga Point on nearby Guadalcanal. By August 1942, the Japanese had about 900 troops on Tulagi and nearby islands, and 2,800 personnel (2,200 of whom were Korean construction workers) on Guadalcanal. These bases, when complete, would protect Japan's major base at Rabaul, threaten Allied supply and communication lines, and establish a staging area for possible future offensives against Fiji, New Caledonia, and Samoa. The Japanese planned to deploy 45 fighters and 60 bombers to Guadalcanal once the airfield was complete.

In preparation for the offensive, in May, 1942, U.S. Major General Alexander Vandegrift moved his U.S. 1st Marine Division to New Zealand. Other Allied land, naval, and air force units were sent to establish bases in Fiji, Samoa, and New Caledonia. Espiritu Santo in New Caledonia became the headquarters and main base for the impending offensive, codenamed Operation Watchtower, with the commencement date set for August 7, 1942. Invaluable information was obtained from coastwatchers who, organised by the Australian naval authorities, had secreted themselves and their wireless sets in the jungle before the Japanese arrived. Essentially, the Coastwatchers carried out a special reconnaissance mission.

More intelligence was added by observation from the air, but only by personal observation after landing was any really reliable and accurate detail possible. The American ULTRA cryptanalysts were able to read some of the Japanese radio traffic. The invasion force worked from hastily prepared mosaics photographed from the air and assembled with speed.

At first, the Allied offensive was planned just for Tulagi and the Santa Cruz Islands, omitting Guadalcanal. However, after Allied reconnaissance discovered the Japanese airfield construction efforts on Guadalcanal, capture of that airfield was added to the plan and the Santa Cruz operation was dropped.

The Allied Watchtower expeditionary force of 75 warships and transports, which included vessels from both the U.S. and Australia, assembled near Fiji on July 26, 1942, and engaged in one rehearsal landing prior to leaving for Guadalcanal on July 31. The rehearsal went poorly. The on-scene commander of the Allied expeditionary force was U.S. Vice Admiral Frank Jack Fletcher, whose flagship was the U.S aircraft carrier Saratoga. The Allied commander of the amphibious transport force was U.S. Rear Admiral Richmond K. Turner. Vandegrift was the commander of the 16,000 Allied (primarily U.S. Marine) ground forces involved in the landings.

Landings

Due to bad weather, the Allied expeditionary force arrived in the vicinity of Guadalcanal undetected by the Japanese on the morning of August 7. The landing force ships split into two groups, with one group assaulting Guadalcanal, and the other Tulagi, Florida, and nearby islands. Allied warships bombarded the invasion beaches while U.S. carrier aircraft bombed Japanese positions on the target islands and destroyed 15 Japanese seaplanes at their base near Tulagi.

Tulagi, and the two nearby, small islands of Gavutu and Tamambogo were assaulted by 3,000 U.S. Marines on August 7. The 886 Imperial Navy personnel on the three islands fiercely resisted the Marine attacks. With some difficulty, the U.S. Marines finally secured all three islands, Tulagi on August 8, and Gavutu and Tanambogo by August 9. All the Japanese defenders were killed as the Marines suffered 122 killed.

In contrast to Tulagi, Gavutu, and Tanambogo, the landings on Guadalcanal encountered much less resistance. At 09:10 on August 7, General Vandegrift and 11,000 Marines came ashore on Guadalcanal between Koli Point and Lunga Point. Advancing towards Lunga Point, they encountered no resistance except for "tangled" rain forest, and halted for the night about 1,000 yards from the Lunga Point airfield. The next day, again against little resistance, the Marines advanced all the way to the Lunga River, and secured the airfield by 16:00 on August 8. The Japanese naval construction units had abandoned the airfield area, leaving behind food, supplies, and intact construction equipment and vehicles.

During the landing operations on August 7 and 8, Japanese aircraft based at Rabaul attacked the Allied amphibious forces several times, setting afire the U.S. transport George F. Elliot (which eventually sank two days later) and heavily damaging the U.S. destroyer Jarvis. In the air attacks over the two days, the Japanese lost 36 aircraft, while the U.S. lost 19 aircraft, both in combat and to accident, including 14 carrier fighter aircraft.

After these clashes, Fletcher was concerned about the losses to his carrier fighter aircraft strength, anxious about the threat to his carriers from further Japanese air attacks, and worried about his ship's fuel levels. Fletcher determined that he would withdraw from the Solomon Islands area with his carrier task forces the evening of August 8 to avoid further losses. Due to the loss of carrier air cover, Turner decided that he would have no choice but also to withdraw his ships from Guadalcanal, even though less than half of the supplies and heavy equipment on the transport ships needed by the troops ashore had been unloaded. Turner intended to unload as many supplies as possible on Guadalcanal and Tulagi throughout the night of August 8 and then depart with his ships early on August 9.

That night, as the transports unloaded, two groups of Allied warships screening the transports were surprised and defeated by a single Japanese force of seven cruisers and one destroyer, commanded by Japanese Vice Admiral Gunichi Mikawa. Three U.S. and one Australian cruisers were sunk and one other U.S. cruiser and two destroyers were damaged in this lopsided Japanese victory. Fortunately for the Allies, Mikawa, who was unaware that Fletcher had withdrawn with the U.S. carriers, immediately returned to his home ports of Rabaul and Kavieng without attempting to attack the now unprotected Allied transports. Mikawa was concerned about U.S. carrier air attacks during daylight hours if he tarried in the southern Solomons area. After this defeat, Turner withdrew all remaining Allied naval forces by the evening of August 9, leaving the Marines ashore without much of the heavy equipment, provisions, and troops still aboard the transports.

Initial Operations

The Marines left ashore on Guadalcanal initially concentrated on forming a defense perimeter around the airfield, moving the landed supplies within the perimeter, and finishing the airfield. Vandegrift placed his 11,000 troops on Guadalcanal in a loose perimeter around the Lunga Point area. In four days of intense effort, the supplies were moved from the landing beach into dispersed dumps within the perimeter. Work began on the airfield immediately, mainly using captured Japanese equipment. On August 12, the airfield was named Henderson Field after Major Lofton Henderson, a Marine aviator who had been killed at the Battle of Midway. By August 18, the airfield was ready for operation. Five days worth of food had been landed from the transports which, along with captured Japanese provisions, gave the Marines a total of 14 days worth of food. Allied troops encountered a "severe strain" of dysentery soon after the landings, with one in five Marines afflicted by mid-August. Although some of the Korean construction workers surrendered to the Marines, most of the remaining Japanese and Korean personnel gathered just west of the Lunga perimeter on the west bank of the Matanikau river and subsisted mainly on coconuts. A Japanese naval outpost was also located at Taivu Point, about 22 miles east of the Lunga perimeter. On August 8, a Japanese destroyer delivered 113 naval reinforcement troops to the Matanikau position.

On the evening of August 12, a 25-man U.S. Marine patrol, led by Lt. Col Frank Goettge and primarily consisting of intelligence personnel, landed by boat west of the Lunga perimeter, between Point Cruz and the Matanikau River, on a reconnaissance mission with a secondary objective of contacting a group of Japanese troops that the U.S. forces believed might be willing to surrender. Soon after the patrol landed, a nearby platoon of Japanese troops attacked and almost completely wiped-out the group of Marines. Goettge, whose body was never found, received a posthumous Medal of Honor.

On August 19, Vandegrift sent three companies from the U.S. 5th Marine Regiment to attack the Japanese troop concentration west of the Matanikau. One Marine company attacked across the sandbar at the mouth of the Matanikau river while another company crossed the river 1,000 yards inland and attacked the Japanese forces located in Matanikau village. The third Marine company landed by boat further west and attacked Kokumbuna village. After briefly occupying the two villages, the three Marine companies returned to the Lunga perimeter, having killed about 65 Japanese soldiers while losing four themselves. This action, sometimes referred to as the "First Battle of the Matanikau," was the first of several major actions that would take place in the Matanikau river area during the campaign.

On August 20, the U.S. escort carrier Long Island delivered two squadrons of Marine aircraft to Henderson Field. One squadron consisted of 19 Grumman F4F fighters and the other was a squadron of 12 SBD Dauntless dive bombers. The aircraft at Henderson became known as the "Cactus Air Force" after the Allied codename for Guadalcanal. The Marine fighters went into action the next day, attacking one of the Japanese bomber air raids that occurred almost daily. On August 22, five U.S. Army P-400 fighters (a variant of the P-39 Airacobra) and their pilots arrived at Henderson Field.

Battle of the Tenaru

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, currently 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 Kiyotaki Kawaguchi was at Palau, the 4th (Aoba) Infantry Regiment was in the Philippines and the 28th (Ichiki) Infantry Regiment, under the command of Colonel Kiyonao Ichiki, was onboard transport ships near Guam. The different units began to move towards Guadalcanal immediately, but Ichiki's regiment, being the closest, would ultimately arrive 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 August 19.

Underestimating the strength of Allied forces on Guadalcanal, Ichiki's unit conducted a nighttime frontal assault on Marine positions at Alligator Creek (often called the "Ilu River" on U.S. Marine maps) on the east side of the Lunga perimeter in the early morning hours of August 21. Ichiki's assault was defeated with heavy losses for the Japanese attackers in what became known as the Battle of the Tenaru. After daybreak, the Marine units counterattacked Ichiki's surviving troops, killing many more of them, including Ichiki. In total, all but 128 of the original 900 of the Ichiki Regiment's First Element were killed in the battle. The survivors of Ichiki's force returned to Taivu Point, notified 17th Army headquarters of their defeat in the battle, and awaited further reinforcements and orders from Rabaul.

Battle of the Eastern Solomons

As the Tenaru battle was ending, more Japanese reinforcements were already on their way from Truk. Departing Truk on August 16 were three slow transports carrying the remaining 1,400 soldiers from Ichiki's (28th) Infantry Regiment plus 500 naval troops from the 5th Yokosuka Special Naval Landing Force. Guarding the transports were 13 warships commanded by Japanese Rear Admiral Raizo Tanaka who planned to land the troops on Guadalcanal on August 24. To cover the landings of these troops and provide support for the operation to retake Henderson Field from Allied forces, the Japanese Combined Fleet sortied from Truk on August 21 and headed towards the southern Solomon Islands with a force of three carriers and 30 other warships.

Simultaneously, the U.S. carrier task forces under Fletcher approached Guadalcanal to counter the Japanese offensive efforts. On August 24 and August 25, the two carrier forces fought the Battle of the Eastern Solomons' that resulted in the fleets of both adversaries retreating from the area after taking some damage, with the Japanese losing one aircraft carrier sunk. Tanaka's convoy, after suffering heavy damage during the battle, including the sinking of one of the transports, was forced, due to the continued threat by U.S. aircraft based at Henderson Field, to divert to the Shortland Islands in the northern Solomons in order for the surviving troops to be transferred to destroyers for later delivery to Guadalcanal.

Air battles over Henderson Field and strengthening of the Lunga defenses

Small numbers of U.S. aircraft and their crews, both fighters and bombers, continued to arrive at Guadalcanal. By the end of August, 64 aircraft of all types were stationed at Henderson Field. On September 3, the commander of 1st Marine Aircraft Wing, U.S. Marine Brigadier General Roy S. Geiger, arrived with his staff and took command of all air operations at Henderson Field. Air battles between the Allied aircraft at Henderson and Japanese bombers and fighters from Rabaul continued, with almost daily engagements between the two adversaries in the skies over Guadalcanal. Between August 26 and September 5, the U.S. lost about 15 aircraft while the Japanese lost approximately 19 aircraft. More than half of the U.S. aircrews, however, were rescued while most of the Japanese aircrews weren't recovered. The eight-hour round trip flight from Rabaul to Guadalcanal (about 1,120 miles total) seriously hampered Japanese efforts to establish air superiority over Henderson Field. Australian coastwatchers on Bougainville and New Georgia islands were usually able to provide Allied intelligence on Guadalcanal with advance notice of inbound Japanese air strikes, allowing the U.S. fighters time to take off and position themselves to ambush the Japanese bombers and fighters as they approached Henderson Field. Thus, the Japanese were slowly losing an air war of attrition over Guadalcanal.

During this time, Vandegrift continued to direct efforts to strengthen and improve the defenses of the Lunga perimeter. Between August 21 and September 3, he relocated three Marine battalions from Tulagi and Gavutu to Guadalcanal. These units added about 1,500 troops to Vandegrift's original 11,000 men defending Henderson Field. The 1st Parachute battalion, which had suffered heavy casualties in the Battle of Tulagi and Gavutu-Tanambogo in August, was placed under Edson's command.

Small Allied naval convoys arrived at Guadalcanal between August 23 and September 8 to provide the Marines at Lunga with more food, ammunition, aircraft fuel, and aircraft technicians. The September 1 convoy also brought 392 U.S. Navy Seabees (construction engineers) to maintain and improve Henderson Field.

Tokyo Express

By August 23, Kawaguchi's 35th Infantry Brigade reached Truk and was loaded onto slow transport ships for the rest of the trip to Guadalcanal. The damage done to Tanka's convoy during Battle of the Eastern Solomons caused the Japanese to reconsider trying to deliver more troops to Guadalcanal by slow transport. Instead, the ships carrying Kawaguchi's soldiers were sent to Rabaul. From there, the Japanese planned to deliver Kawaguchi's men to Guadalcanal by destroyers staging through a Japanese naval base in the Shortland Islands. The Japanese destroyers were usually able to make the round trip down "The Slot" to Guadalcanal and back in a single night, thereby minimizing their exposure to Allied air attack. However, delivering the troops in this manner prevented most of the soldier's heavy equipment and supplies, such as heavy artillery, vehicles, and much food and ammunition, from being carried to Guadalcanal with them. These high speed destroyer runs to Guadalcanal, which occurred throughout the campaign, were later called the "Tokyo Express" by Allied forces and "Rat Transportation" by the Japanese. Due to either the inability or unwillingness of Allied naval commanders to challenge Japanese naval forces at night, the Japanese controlled the seas around the Solomon Islands during the nighttime. However, any Japanese ship remaining within range of the aircraft at Henderson Field during the daylight hours (about 200 miles) was in great danger from damaging air attack. This "curious tactical situation" would exist for the next several months during the campaign.

Between August 29 and September 4 various Japanese light cruisers, destroyers, and patrol boats landed almost 5,000 troops at Taivu Point, including most of the 35th Infantry Brigade, much of the Aoba (4th) Regiment, and the rest of Ichiki's regiment. General Kawaguchi, who landed at Taivu Point on the August 31 Express run, was placed in command of all the Japanese troops on Guadalcanal. A barge convoy took another 1,000 soldiers of Kawaguchi's brigade, under the command of Colonel Akinosuka Oka, to Kamimbo, west of the Lunga perimeter.

Battle of Edson's Ridge

On September 7, Kawaguchi issued his attack plan to "route and annihilate the enemy in the vicinity of the Guadalcanal Island airfield." Kawaguchi's attack plan called for his forces, split into three divisions, to approach the Lunga perimeter inland, culminating with a surprise night attack. Oka's forces would attack the perimeter from the west while Ichiki's Second Echelon, now renamed the Kuma Battalion, would attack from the east. The main attack would be by Kawaguchi's "Center Body," numbering 3,000 men in three battalions, from the south of the Lunga perimeter.By September 7, most of Kawaguchi's troops had departed Taivu to begin marching towards Lunga Point along the coastline. About 250 Japanese troops remained behind to guard the brigade's supply base at Taviu.

Meanwhile, native island scouts brought reports to the U.S. Marines of Japanese troops at Taivu, near the village of Tasimboko. Edson planned a raid to "wipe-out" the Japanese troop concentration at Taivu. On September 8, after being dropped-off near Taivu by boat, Edson's men captured Tasimboko as the Japanese defenders retreated into the jungle. In Tasimboko, Edson's troops discovered "vast stockpiles" of food, ammunition, medical supplies, and a powerful shortwave radio. After destroying everything in sight, except for some documents and equipment carried back with them, the Marines returned to the Lunga perimeter. The mounds of supplies, along with intelligence gathered from the captured documents, informed the Marines that at least 3,000 Japanese troops were on the island and apparently planning an attack on the U.S. defenses.

Edson believed that the Japanese attack would come at a narrow, grassy, 1,000-yard-long, coral ridge that paralleled the Lunga River and was located just south of Henderson Field. The unnamed ridge offered a natural avenue of approach to the airfield, commanded the surrounding area and, at that time, was almost undefended. On September 11, the 840 men of Edson's battalion deployed onto and around the ridge and prepared to defend it.

On the night of September 12, Kawaguchi's 1st Battalion attacked the Raider's between the Lunga River and ridge, forcing one Marine company to fall back to the ridge. The next night, Kawaguchi faced Edson's 830 Raiders with 3,000 troops of his brigade, plus an assortment of light artillery. The Japanese attack began just after nightfall, with Kawaguchi's 1st battalion assaulting Edson's right flank, just to the west of the ridge. After breaking through the Marine lines, the battalion's assault was eventually stopped by Marine units guarding the northern part of the ridge.

Two companies from Kawaguchi's 2nd battalion charged up the southern edge of the ridge and pushed Edson's troops back to Hill 123 on the center part of the ridge. Throughout the night, Marines at this position, supported by artillery, defeated wave after wave of frontal Japanese attacks. Japanese units that infiltrated past the ridge to the edge of the airfield were also repulsed. Attacks by the Kuma battalion and Oka's unit at other locations on the Lunga perimeter were also defeated by the Marine defenses. On September 14, Kawaguchi led the survivors of his shattered brigade on a five day march west to the Matanikau Valley to join with Oka's unit. In total, Kawaguchi's forces lost about 850 killed and the Marines 104.

On September 15, General Hyakutake at Rabaul learned of Kawaguchi's defeat and forwarded the news to the Imperial General Headquarters in Japan. In an emergency session, the top Japanese army and navy command staffs concluded that, "Guadalcanal might develop into the decisive battle of the war." The results of the battle now began to have a telling strategic impact on Japanese operations in other areas of the Pacific. Hyakutake realized that in order to send sufficient troops and materiel to defeat the Allied forces on Guadalcanal, he could no longer at the same time support the major Japanese offensive currently ongoing on the Kokoda Track in New Guinea. Hyakutake, with the concurrence of the General Headquarters, ordered his troops on New Guinea, who were within 30-miles of their objective of Port Moresby, to withdraw until the "Guadalcanal matter" was resolved. Hyakutake prepared to send more troops to Guadalcanal for another attempt to recapture Henderson Field.

Reinforcement

As the Japanese regrouped west of the Matanikau, the U.S. forces concentrated on shoring up and strengthening their Lunga defenses. On September 14, Vandegrift moved another battalion, the 3rd Battalion, 2nd Marine Regiment (3/2), from Tulagi to Guadalcanal. On September 18, an Allied naval convoy delivered 4,157 men from the 3rd Provisional Marine Brigade (the 7th Marine Regiment plus a battalion from the 11th Marine Regiment and some additional support units), 137 vehicles, tents, aviation fuel, ammunition, rations, and engineering equipment to Guadalcanal. These reinforcements allowed Vandegrift, beginning on September 19, to establish an unbroken line of defense completely around the Lunga perimeter. While covering this convoy, the U.S. aircraft carrier Wasp was sunk by a Japanese submarine southeast of Guadalcanal, temporarily leaving only one Allied aircraft carrier (Hornet) in operation in the South Pacific area. Vandegrift also made some changes in the senior leadership of his combat units, transferring several officers off the island that didn't meet his performance standards, and promoting junior officers who had "proved themselves" to take their places. One of these was the recently promoted Colonel Merritt Edson, who was placed in command of the 5th Marine Regiment.

A lull occurred in the air war over Guadalcanal, with no Japanese air raids occurring between September 14 and September 27 due to bad weather, during which both sides reinforced their prospective air units. The Japanese delivered 85 fighters and bombers to their air units at Rabaul while the U.S. brought 23 fighters and attack aircraft to Henderson Field. On September 20, the Japanese counted 117 total aircraft at Rabaul while the Allies tallied 71 aircraft at Henderson Field. The air war resumed with a Japanese air raid on Guadalcanal on September 27, which was contested by U.S. Navy and Marine fighters from Henderson Field.

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 September 11, too late to join Kawaguchi's attack on the U.S. Marines. By now, though, the battalion had joined Oka's forces near the Matanikau. Tokyo Express runs in mid-September by eight destroyers brought food and ammunition, as well as 280 more soldiers. The Japanese 38th Division in the Dutch East Indies was notified to move to Rabaul in preparation for deployment to Guadalcanal.

Action along the Matanikau

On 23 September, the Marines began a drive to establish defensive positions along the Mantanikau River. A land attack was combined with a small amphibious landing on the flank, but the operation was repulsed by the Japanese.

Battleship bombardment of Henderson Field

A lull in the fighting occurred as the Japanese prepared for a new attack. The Japanese Navy, led by battleships Kongō and Haruna, bombarded the airfield with special fragmentation shells on 13 and 14 October in an attempt to suppress the aircraft operating from the base. The airfield suffered heavy damage, but was returned to service.

Battle for Henderson Field

Finally on 23 October, with the addition of more troops, the Japanese made another attempt to capture Henderson Field] from the south. The newly arrived U.S. Army's 164th Infantry Regiment and the Marines' 1st Battalion, 7th Marine Regiment repulsed the attack. The Japanese 29th Infantry Regiment lost 553 killed or missing and 479 wounded among its 2,554 men. Total American estimates for Japanese casualties on that ridge were 2,200.

Naval Battle of Guadalcanal

In November the Japanese sent reinforcements in the form of the 38th Infantry Division. During the Naval Battle of Guadalcanal, however, the transports carrying this reinforcement were badly damaged and the division was reduced to the strength of a regiment. Through November, American forces continued its offensive in an attempt to push the perimeter out beyond artillery range of the airfield. The Mantanikau River area was finally cleared after overcoming strong Japanese resistance.

Final Allied offensives and Operation Ke

By December the weary 1st Marine Division was withdrawn for recuperation, and over the course of the next month the Marines' XIV Corps took over operations on the island. This corps consisted of the 2nd Marine Division, the U.S. Army's 25th Infantry Division, and its Americal Division.

Japanese strength on the island waned due to attrition and shortages of supplies. Despite the vital role played by intercepted Japanese radio messages using ULTRA, Allied intelligence completely failed to predict or detect the successful Japanese evacuation of Guadalcanal in February 1943. The Japanese inserted a deceptive element into the evacuation plan, but the mistaken assumption that the Japanese were about to mount an offensive led the Allies to believe the Japanese did not consider evacuation to be an option. As an episode in intelligence this shows that assumptions and preconceptions can inhibit the interpretation of data, resulting in this case in one of the worst Allied intelligence failures in the Pacific theater during World War II. The American XIV Corps began offensive operations on 10 January, 1943, but by 8 February they the remaining Japanese had been secretly evacuated.

The lack of supply on both sides meant that combat was especially intense and characterized by extreme desperation. The Japanese used fear as a tactic by placing the severed heads of dead Americans on pikes and planting them around the Marine perimeter. Additionally, neither side took many prisoners. Disease also played a significant role in the ground campaign, as both the Japanese and American forces were weakened by malaria in the insect-infested jungles. Both sides had difficulty maintaining their supplies to the island, the Japanese particularly, to the extent that island became also known as 'Starvation Island' to them.

Aftermath and historical significance

The Battle of Midway is widely considered to be the turning point in the Pacific theater, as it was a strategic naval victory which stopped Japan's eastern expansion toward Hawaii and the U.S. west coast. However, the Empire of Japan continued to expand in the southern Pacific, until receiving two decisive defeats at the hands of the Allies. Australian land forces had defeated Japanese marines in New Guinea at the Battle of Milne Bay in September 1942, which was the first land defeat suffered by the Japanese in the Pacific. And, by the end of 1942, it was clear that Japan also had lost the Guadalcanal campaign, a more serious blow to Japan's strategic plans and an unanticipated defeat at the hands of the Americans.

The Guadalcanal campaign was costly to Japan both strategically and in material losses. Japan lost control of the Solomon Islands and the ability to interdict Allied shipping to Australia. Japan's major base at Rabaul was now directly threatened by allied air power. Most importantly, scarce Japanese land, air, and naval forces had disappeared forever into the Guadalcanal jungle and surrounding sea. The Japanese aircraft and ships destroyed and sunk in this campaign were irreplaceable, as were their highly-trained and veteran crews. It thus can be argued that this Allied victory was the first step in a long string of successes that eventually led to the surrender of Japan.

The Battle of Guadalcanal was one of the first prolonged campaigns in the Pacific. The campaign was a battle of attrition that strained the logistical capabilities of both sides. For the U.S. this need prompted the development of effective combat air transport for the first time. Japan was forced to rely on reinforcement by barges, destroyers, and submarines, with very uneven results. Early in the campaign the Americans were hindered by a lack of resources due to the "Germany First" policy of the United States. However, as the campaign continued, and the American public became more and more aware of the plight and perceived heroism of the American forces on Guadalcanal, more forces were dispatched to the area. This spelled trouble for Japan as its military-industrial complex was unable to match the output of American industry and manpower. Thus, as the campaign wore on the Japanese were losing irreplaceable units while the Americans were rapidly replacing and even augmenting their forces.

After Guadalcanal the Japanese were clearly on the defensive in the Pacific. The constant need to reinforce Guadalcanal had weakened Japanese efforts in other theatres, contributing to a successful Australian counteroffensive in New Guinea which culminated in the capture of the key bases of Buna and Gona in early 1943. In June, the Allies launched Operation Cartwheel, which initiated a strategy of isolating the major Japanese forward base, at Rabaul, and concentrated on cutting its sea lines of communication. This prepared the way for the island hopping campaigns of General Douglas MacArthur in the South West Pacific and Admiral Chester Nimitz in the Central Pacific towards Japan.

According to Weinberg (1995), Guadalcanal's broader effect on the war has often been overlooked. Japan's leaders planned a major offensive in the Indian Ocean and so notified their German ally, but the ships and planes required for the undertaking were instead drained into the Guadalcanal quagmire. At the time Guadalcanal began, Britain was struggling to hold the Germans away from the Suez Canal. Resupply and reinforcements who contributed to the victory at El Alamein could be sent because the Indian Ocean was still open to Allied shipping.

In addition, vital Lend Lease supplies from the U.S were able to travel through the Indian Ocean and across Iran just as the Soviet Union was struggling to stop the German invasion.