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The Battle of the Tenaru, sometimes called the Battle of the Ilu River or the Battle of Alligator Creek, was a land battle between the Imperial Japanese Army and Allied ground forces that took place on August 21, 1942 on the island of Guadalcanal during the Pacific campaign of World War II. The battle was the first major Japanese land offensive during the Guadalcanal campaign. In the battle, U.S. Marines, under the overall command of U.S. Major General Alexander Vandegrift, repulsed an assault by the "First Element" of the "Ichiki" Regiment, under the command of Japanese Colonel Kiyonao Ichiki. The Marines were defending the Lunga perimeter, which guarded Henderson Field, which was captured by the Allies in landings on Guadalcanal on August 7. Ichiki's unit was sent to Guadalcanal in response to the Allied landings with the mission of recapturing the airfield and driving the Allied forces off the island. Underestimating the strength of Allied forces on Guadalcanal, which at that time numbered about 11,000 personnel, Ichiki's unit conducted a nighttime frontal assault on Marine positions at Alligator Creek on the east side of the Lunga perimeter. Ichiki's assault was defeated with heavy losses for the Imperial attackers. The Marine units counterattacked Ichiki's surviving troops after daybreak, killing many more of them. All but 128 of the original 917 of the Ichiki Regiment's First Element were killed in the battle. The battle was the first of three separate major land offensives by the Japanese in the Guadalcanal campaign. The Japanese realized after Tenaru that Allied forces on Guadalcanal were much greater in number than originally estimated and sent larger forces to the island for their subsequent attempts to retake Henderson Field. ==Background== On August 7, 1942, U.S. forces 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, and to secure the islands as starting points for a campaign with the eventual goal of isolating the major Japanese base at Rabaul while also supporting the Allied New Guinea campaign. The landings initiated the six-month-long Guadalcanal campaign.〔Hogue, ''Pearl Harbor to Guadalcanal'', p. 235–236.〕 Taking the Japanese by surprise, the Allied landing forces accomplished their initial objectives of securing Tulagi and nearby small islands, as well as an airfield under construction at Lunga Point on Guadalcanal, by nightfall on August 8.〔Morison, ''Struggle for Guadalcanal'', pp. 14–15.〕 That night, as the transports unloaded, the Allied warships screening the transports were surprised and defeated by an Imperial fleet 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 the Battle of Savo Island. Turner withdrew all remaining Allied naval forces by the evening of August 9 without unloading all of the heavy equipment, provisions, and troops from the transports, although most of the divisional artillery was landed, consisting of 32 75 mm and 105 mm howitzers. Only five days worth of rations were landed.〔Zimmerman, ''The Guadalcanal Campaign'', p. 49–56.〕〔Smith, ''Bloody Ridge'', p. 11 & 16.〕 The Marines 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. Captured Japanese stock increased the total supply of food to 14 days worth. To conserve the limited food supplies, the Allied troops were limited to two meals per day.〔Shaw, ''First Offensive'', p. 13.〕〔Smith, ''Bloody Ridge'', p. 16–17.〕 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 Kiyotake 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 at sea en route to Japan from Guam.〔Miller, ''The First Offensive'', p. 96〕 The different units began to move towards Guadalcanal immediately, but Ichiki's regiment, being the closest, arrived first.〔Smith, ''Bloody Ridge'', p. 88, Evans, ''Japanese Navy'', p. 158, and Frank, ''Guadalcanal'', p. 141–143. The Ichiki regiment was named after its commanding officer and was part of the 7th Division from Hokkaido. The Aoba regiment, from the 2nd Division, took its name from Aoba Castle in Sendai, because most of the soldiers in the regiment were from Miyagi prefecture (Rottman, ''Japanese Army'', p. 52). Ichiki's regiment had been assigned to invade and occupy Midway Atoll, but were on their way back to Japan after the invasion was cancelled following the Japanese defeat in the Battle of Midway. Although some histories state that Ichiki's regiment was at Truk, Raizo Tanaka, in Evans' book, states that he dropped off Ichiki's regiment at Guam after the Battle of Midway. Ichiki's regiment was subsequently loaded on ships for transport elsewhere but were rerouted to Truk after the Allied landings on Guadalcanal.〕 An aerial reconnaissance of the U.S. Marine positions on Guadalcanal on August 12 by one of the senior Japanese staff officers from Rabaul sighted few U.S. troops in the open and no large ships in the waters nearby, convincing Imperial Headquarters that the Allies had withdrawn the majority of their troops. In fact, none of the Allied troops had been withdrawn.〔Frank, ''Guadalcanal'', p. 143–144.〕 Hyakutake issued orders for an advance unit of 900 troops from Ichiki's regiment to be landed on Guadalcanal by fast warship to immediately attack the Allied position and reoccupy the airfield area at Lunga Point. The remaining personnel in Ichiki's regiment would be delivered to Guadalcanal by slower transport later. At the major Japanese naval base at Truk, which was the staging point for delivery of Ichiki's regiment to Guadalcanal, Colonel Ichiki was briefed that 2,000–10,000 U.S. troops were holding the Guadalcanal beachhead and that he should, "avoid frontal attacks."〔Evans, ''Japanese Navy'', p. 161, Griffith, ''Battle for Guadalcanal'', p. 98–99 and Smith, ''Bloody Ridge'', p. 31.〕 Ichiki and 916 of his regiment's 2,300 troops, designated the "First Element" and carrying seven days' supply of food, were delivered to Taivu Point, about east of Lunga Point, by six destroyers at 01:00 on August 19.〔Evans, ''Japanese Navy'', p. 161, Frank, ''Guadalcanal'', p. 145, Jersey, ''Hell's Islands'', p. 204, 212, Morison, ''Struggle for Guadalcanal'', p. 70, and Smith, ''Bloody Ridge'', p. 43. The First Element troops were mainly from the 28th's 1st Battalion under a Major Kuramoto and were mostly from Asahikawa, Hokkaidō. At Taivu Point was an Imperial outpost with about 200 naval personnel who assisted with the unloading of Ichiki's forces from the destroyers.〕 Ichiki was ordered to scout the American positions and wait for the remainder of his force to arrive. Known as the ''Ichiki Butai'' (Ichiki Detachment), they were an elite and battle-seasoned force but as was about to be discovered, they were heavily stricken with "victory disease" - otherwise known as overconfidence due to previous success. Ichiki was so confident in the superiority of his men that he decided to destroy the American defenders before the remaining majority of his force arrived, even writing in his journal "''18 August, landing; 20 August, march by night and battle; 21 August, enjoyment of the fruit of victory''".〔Spector, ''Eagle Against the Sun'', p. 496〕 He concocted a brazenly simple plan: march straight down the beach and through the American defenses.〔Gilbert, ''Marine Tank Battles in The Pacific'', p. 41〕 Leaving about 100 personnel behind as a rear guard, Ichiki marched west with the remaining 800 men of his unit and made camp before dawn about east of the Lunga perimeter. The U.S. Marines at Lunga Point received intelligence that a Japanese landing had occurred and took steps to find out exactly what was happening.〔Griffith, ''Battle for Guadalcanal'', p. 99–100 and Smith, ''Bloody Ridge'', p. 29 & 43–44.〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Battle of the Tenaru」の詳細全文を読む スポンサード リンク
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