The Battle of Edson's Ridge, also known as the Battle of the Bloody Ridge, Battle of Raiders Ridge, and Battle of the Ridge, was a land battle of the Pacific campaign of World War II between the Imperial Japanese Army and Allied (mainly United States Marine Corps) ground forces. It took place from 12 to 14 September 1942, on Guadalcanal in the Solomon Islands, and was the second of three separate major Japanese ground offensives during the Guadalcanal campaign.
In the battle, U.S. Marines under the overall command of U.S. Major General Alexander Vandegrift repulsed an attack by the Japanese 35th Infantry Brigade under the command of Japanese Major General Kiyotake Kawaguchi. The Marines were defending the Lunga perimeter that guarded Henderson Field on Guadalcanal, which was captured from the Japanese by the Allies in landings on Guadalcanal on 7 August 1942. Kawaguchi's unit was sent to Guadalcanal in response to the Allied landings with the mission of recapturing the airfield and driving the Allied forces from the island.
Underestimating the strength of Allied forces on Guadalcanal—over 12,000 men—Kawaguchi's 6,000 soldiers conducted several nighttime frontal assaults on the U.S. defenses. The main Japanese assault occurred around Lunga ridge south of Henderson Field, defended by troops from several U.S. Marine Corps units, primarily troops from the 1st Raider and 1st Parachute Battalions under the command of Lieutenant Colonel Merritt A. Edson. Although the Marine defenses were almost overrun, Kawaguchi's attack was ultimately defeated after fierce fighting, with heavy losses for the Japanese.
Because of the key participation by Edson's unit in defending the ridge, the ridge was commonly referred to as "Edson's" ridge in historical accounts of the battle in Western sources.Jersey, Hell's Islands, p. 224. After Edson's Ridge, the Japanese continued to send troops to Guadalcanal for further attempts to retake Henderson Field, affecting Japanese offensive operations in other areas of the South Pacific. According to the participants on both sides, Edson's Ridge was the closest the Japanese came to winning the overall battle for Guadalcanal.
Background Guadalcanal campaign On 7 August 1942, Allied forces (primarily U.S.) landed on Guadalcanal, Tulagi, and Florida Islands in the Solomon Islands. 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. They were also intended to secure the islands as starting points for a campaign to neutralize the major Japanese base at Rabaul and support the Allied New Guinea campaign. The landings initiated the six-month-long Guadalcanal campaign.Hogue, Pearl Harbor to Guadalcanal, pp. 235–236.
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 under construction at Lunga Point () on the north shore of the island of Guadalcanal, east of the present day capital of Honiara.Morison, Struggle for Guadalcanal, pp. 14–15. By 9 August, 10,900 troops from Major General Alexander Vandegrift's 1st Marine Division were on Guadalcanal, occupying a loose perimeter around the Lunga Point area.Miller, Guadalcanal: The First Offensive, pp. 75.
On 12 August, the airfield was named Henderson Field after Major Lofton Henderson, a Marine aviator who had been killed at the Battle of Midway. The Allied aircraft and pilots that subsequently operated out of Henderson Field were called the "Cactus Air Force" after the Allied code name for Guadalcanal.Shaw, First Offensive, p. 13.
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 () under the command of Lieutenant-General Harukichi Hyakutake—with the task of retaking Guadalcanal from Allied forces. The 17th Army, already 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 Infantry Regiment under Colonel Kiyonao Ichiki was embarked on transport ships near Guam. The different units began to move toward Guadalcanal immediately; Ichiki's regiment, the closest, arrived first. The "First Element" of Ichiki's unit—consisting of about 917 soldiers—landed from destroyers at Taivu Point (), about east of the Lunga perimeter, on 19 August.Smith, Bloody Ridge, p. 187
Underestimating the strength of Allied forces on Guadalcanal, Ichiki's First Element conducted a nighttime frontal assault on Marine positions at Alligator Creek on the east side of the Lunga perimeter in the early morning hours of 21 August. Ichiki's assault was repulsed with devastating losses for the attackers in what became known as the Battle of the Tenaru: all but 128 of the 917 men of the First Element (including Ichiki) were killed in the battle. The survivors returned to Taivu Point, notified 17th Army headquarters of their defeat in the battle and awaited further reinforcements and orders from Rabaul.Frank, Guadalcanal, pp. 156–158, 681.
By 23 August, Kawaguchi's unit had reached Truk and was loaded onto slow transport ships for the rest of the trip to Guadalcanal. Because of the damage caused by Allied air attack to a separate troop convoy during the Battle of the Eastern Solomons, the Japanese decided not to deliver Kawaguchi's troops to Guadalcanal by slow transport ship; 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, minimizing their exposure to Allied air attack. However, most of the soldiers' heavy equipment and supplies, such as heavy artillery, vehicles, and much food and ammunition, could not be taken 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.Griffith, Battle for Guadalcanal, p. 113 and Frank, Guadalcanal, pp. 198–199, 205, 266.
The Japanese controlled the seas around the Solomon Islands during the nighttime and were not challenged by the Allies. However, any Japanese ship remaining within the range of the aircraft at Henderson Field in daylight was in great danger from air attacks. This "curious tactical situation" held for several months.Morison, Struggle for Guadalcanal, pp. 113–114.
Troop movement On 28 August 600 of Kawaguchi's troops were loaded onto the destroyers , , , and , designated Destroyer Division 20 (DesDiv20). Because of a shortage of fuel, DesDiv20 could not make the entire round trip to Guadalcanal at high speed in one night and had to start the trip earlier in the day so that they could complete the trip by the next morning at a slower speed which conserved fuel. At 18:05 that day, 11 U.S. dive bombers from VMSB-232, under the command of Lt. Col. Richard Mangrum,Hulber and DeChant, Flying Leathernecks, p. 49. flew from Henderson Field and located and attacked DesDiv20 about north of Guadalcanal, sinking Asagiri and heavily damaging Yugiri and Shirakumo. Amagiri took Shirakumo in tow and the three destroyers returned to the Shortlands without completing their mission. The attack on DesDiv20 killed 62 of Kawaguchi's soldiers and 94 crew members.Griffith, Battle for Guadalcanal, p. 114; Frank, Guadalcanal, pp. 199–200; and Smith, Bloody Ridge, p. 98.
Subsequent "Tokyo Express" runs were more successful. Between 29 August and 4 September, various Japanese light cruisers, destroyers, and patrol boats were able to land almost 5,000 troops at Taivu Point, including all of the 35th Infantry Brigade, one battalion of the Aoba Regiment, and the rest of Ichiki's regiment. General Kawaguchi, who landed at Taivu Point on 31 August, was placed in command of all the Japanese troops on Guadalcanal.Frank, Guadalcanal, pp. 201–203; Griffith, Battle for Guadalcanal, pp. 116–124; and Smith, Bloody Ridge, pp. 87–112.
On the night of 4/5 September, as three of the destroyers—, , and —prepared to shell Henderson Field after landing their troops, they detected and sank two U.S. ships in the vicinity, the small, old destroyer transports (called "APDs" by the U.S. Marines) and that were used to shuttle Allied troops around the Guadalcanal/Tulagi area.Frank, Guadalcanal, pp. 211–212; Peatross, Bless 'em All, pp. 91–92; and Morison, Struggle for Guadalcanal, pp. 118–121.
In spite of the successes of the destroyer runs, Kawaguchi insisted that as many soldiers of his brigade as possible be delivered to Guadalcanal by slow barges. Therefore, a convoy carrying 1,100 of Kawaguchi's troops and heavy equipment in 61 barges, mainly from the 2nd Battalion, 124th Infantry Regiment under the command of Colonel Akinosuka Oka, departed the northern coast of Santa Isabel Island on 2 September. On 4–5 September, aircraft from Henderson Field attacked the barge convoy, killing about 90 of the soldiers in the barges and destroying much of the unit's heavy equipment. Most of the remaining 1,000 troops were able to land near Kamimbo (), west of the Lunga perimeter over the next few days.Alexander, pp. 138–139; Griffith, Battle for Guadalcanal, pp. 116–124; Frank, Guadalcanal, p. 213; and Smith, Bloody Ridge, pp. 106–109. Griffith says 400 troops were killed, Frank and Smith say 90 were killed. Oka commanded the entire 124th Regiment so his command section was attached to the 2nd Battalion at this time. The 2nd Battalion's commander, Major Takamatsu, was killed during the air attacks on the barge convoy. By 7 September, Kawaguchi had 5,200 troops at Taivu Point and 1,000 west of the Lunga perimeter.Frank, Guadalcanal, p. 219. Kawaguchi was confident enough that he could defeat the Allied forces facing him that he declined an offer from the 17th Army for delivery of one more infantry battalion to augment his forces. Kawaguchi believed that there were only about 2,000 U.S. Marines on Guadalcanal.Frank, Guadalcanal, p. 218.
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), and the 1st Parachute Battalion—from Tulagi and Gavutu to Guadalcanal. These units added about 1,500 troops to Vandegrift's original 11,000 men defending Henderson Field.Peatross, Bless 'em All, p. 91; Morison, Struggle for Guadalcanal, p. 15; and Hough, Pearl Harbor to Guadalcanal, p. 298. U.S. transport destroyer was sunk by Japanese aircraft off Guadalcanal on 30 August, after delivering Company D of the 1st Raiders, with 51 of her crew killed. 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.Christ, p. 176; Smith, Bloody Ridge, p. 103. The Parachutists were delivered to Guadalcanal on 2 September.
Battle Prelude Kawaguchi set the date for his attack on the Lunga perimeter for 12 September and began marching his forces west from Taivu towards Lunga Point on 5 September. He radioed 17th Army and requested that it carry out air strikes on Henderson Field beginning on 9 September and that naval warships be stationed off Lunga Point on 12 September to "destroy any Americans who attempted to flee from the island."Smith, Bloody Ridge, p. 112–113.