New Georgia counterattack

Due to the decision by U.S. commanders to land at Zanana in early July, rather than further west along the coast, the American lines of communication became stretched and vulnerable as the advance towards Munda continued. Meanwhile, the inexperienced American troops were disorganized and suffering from poor morale and bad leadership, having become bogged down by harsh terrain and bad weather, which had quickly turned the jungle tracks into mud.[27] Sasaki launched his counterattack at the moment that the U.S. advance halted to reorganize.[28][21] The objective of the Japanese operation was to destroy the American forces on New Georgia by attacking their exposed flank and rear areas. It was intended that the attack would be coordinated with naval operations to cut off the American troops on New Georgia and air attacks on Allied logistical bases on the island elsewhere.[29]

Sensing an advantage, Sasaki ordered the 13th Infantry Regiment to penetrate the U.S. right flank around the upper reaches of the Barike River and attack their rear elements, while elements of the 229th which were already occupying defensive positions along the front attacked the left flank.[28][30] A total of six companies from two battalions of the 13th Infantry Regiment were committed to this effort, while the regiment's 2nd Battalion remained around Bairoko. These troops began moving from their assembly area in a plantation 5 miles (8.0 km) north of Munda on 14 July.[23]

Battle map depicting the battlefield shortly after the Japanese counterattack of 17/18 July

While Tomonari's troops began their march, those of Hirata's 229th in the center of the line undertook a series of patrols and minor attacks to keep the U.S. forces off balance.[31] Hampered by the terrain just as the U.S. troops had been, it took three days for Tomonari's troops to complete their preliminary move.[32][33] From the Barike, the Japanese began probing the Allied right flank, which was only lightly held by isolated outposts, before moving towards an assembly area for the main assault. Track improvement had not been completed in this area and, as a result, the U.S. outposts could not be reinforced quickly. Sasaki planned for Tomonari's forces to infiltrate this area and sever the supply lines from Zanana while Hirata's 229th Infantry Regiment advanced from Munda to assault the center and right of the U.S. line. In doing so, the Japanese hoped to complete an envelopment of the U.S. regiments holding the front. The element of surprise was lost, however, when U.S. patrols detected the infiltration. In the afternoon of 17 July, elements of the U.S. 43rd Cavalry Reconnaissance Troop unsuccessfully attempted an ambush but were overwhelmed in the attempt.[30][34]

Despite the Japanese commander's intentions to coordinate the efforts of the forces assigned to the counterattack, ultimately this was not achieved as the Japanese force lacked communications equipment. Japanese preparations were also disrupted by U.S. artillery fire around 11:30 on 17 July, which landed on the forward positions of the 229th Infantry Regiment just prior them forming up for the assault in the center of the U.S. line and this ultimately delayed their attack. Artillery and air strikes also broke up an effort by naval troops from the Yokosuka 7th Special Naval Landing Force to launch an amphibious landing behind the Allied front.[34][31] Throughout 17 July, the 229th was kept off balance around the Laiana beachhead by the U.S. 172nd Infantry Regiment with well coordinated close armored support from several Marine Corps tanks, while the U.S. 169th Infantry Regiment carried out a local attack between Reincke Ridge and Kelley Hill with two battalions which kept the Japanese in contact throughout the day.[34][35]

Meanwhile, at around 16:00, the 13th Infantry Regiment reached a mangrove swamp on the bank of the Barike River, where they began to assemble for the attack on the beachhead.[31] The rear area of the U.S. beachhead consisted of many spread out camps and facilities that were mainly occupied by logistics, support and technical troops. Throughout the night of 17–18 July, formed into small section or platoon-sized groups,[36] the Japanese succeeded in infiltrating and attacking several isolated outposts in the American rear areas, which were hastily defended by small groups of support troops. Over several hours, they carried out minor raids against supply dumps and engineer depots, and ambushed medical parties, inflicting many casualties on the American forces. During the confused fighting, the Japanese raiders destroyed vital telephone switchboards in an effort to disrupt communications. Nevertheless, the US forces were able to maintain communications with their supporting artillery battalions through a single telephone and throughout the night the artillery liaison officer called down heavy barrages from offshore batteries in response, some within 150 yards (140 m) of the divisional command post.[28][37]

US reinforcements landing around Munda in the aftermath of the Japanese counterattack

Although the attack in the rear areas continued throughout the night, the artillery fire prevented the Japanese from being able to concentrate in strength. The beachhead area was also attacked, but a force of 52 Marines from the 9th Defense Battalion commandeered two U.S. Army .30 caliber machine guns and occupied a defensive position on a knoll about 150 yards (140 m) inland, supported by an anti-tank platoon and an ad hoc force of another fifty service troops and artillerymen. From this position, at around 21:00 they ambushed a force of Japanese attackers moving from the command post to set up a mortar, while others manned the unit's antiaircraft guns. The Japanese made four efforts to push through the ambush, but ultimately withdrew, leaving at least 18 of their number dead.[28][38] Other raiders attacked kitchen areas and medical facilities, including casualty clearing stations. At one aid station, several patients fought back, killing four Japanese.[39] In other stations, the medics and doctors attempted to fight off Japanese infantrymen who bayoneted patients in their beds.[36]

In the center of the line, and further to the south, just after midnight on 17–18 July, two battalions (the 2nd and 3rd) from Hirata's 229th Infantry Regiment began a series of attacks against elements of the US 169th Infantry Regiment.[40] After the initial attack against the 1st Battalion, 169th Infantry Regiment around Kelley Hill failed, the second effort began well for the Japanese who were able to skillfully advance close to the line in places to hurl grenades into the US front line. Mortar fire attempted to flush these troops out, and eventually the Japanese effort in the center of the lines was fought to a standstill as the defending troops used the high ground to their advance, calling down accurate artillery barrages down on the attacking troops, of which at least 102 were killed.[37] Two hundred men from the Japanese 1st Battalion, 229th Infantry Regiment, which had been withdrawing from the Segi area following earlier fighting around Viru Harbor, stumbled into the area and also joined in the attack against a company of the U.S. 169th Infantry Regiment.[22] An assault against the 3rd Battalion, 103rd Infantry Regiment, which had been assigned to support the 172nd Infantry Regiment around the beach area, was also beaten back.[40][37]

Griswold urgently requested reinforcements. A battery was dispatched to Zanana from Kokorana and the 148th Infantry Regiment began preparations to move from Rendova at first light.[37] Ultimately, though, the attack on the beachhead petered out and the 13th Infantry Regiment melted into the jungle during the morning of 18 July. They would remain scattered in small numbers, and in the aftermath of the attack continued to harass U.S. troops. Sasaki hoped to be able to mount another effort to go on the offensive, but ultimately this opportunity did not eventuate.[41]

According to the historian Eric Hammel, "the action cost both sides many lives", although exact casualty numbers are not specified.[42] The US Army official historian John Miller Jr. judged that the Japanese 13th Infantry Regiment's attacks "caused a few casualties but accomplished very little, certainly not enough to justify its trip from Kolombangara".[37]

The first U.S. fighter aircraft lands at Munda Airfield, 14 August

The arrival of U.S. reinforcements began early on 18 July, with elements of the 148th Infantry Regiment landing at Zanana. Having hurriedly embarked at Rendova, they had been told to expect to fight as soon as they landed, but the fighting around the beach had concluded by the time they arrived. They were quickly pushed inland by U.S. commanders to shore up their vulnerable right flank and open the Munda Trail; during this movement the regiment's advanced elements clashed several times with small groups of Japanese infantry. Efforts to relieve the 169th took several days, with minor actions continuing until 20 July, including an ambush around one of the bridges across the Barike.[39] In the coming days both the 145th and 161st Infantry Regiments arrived, and deployed opposite three battalions from the Japanese 229th Infantry, and a company from the 230th.[40]

After the Japanese counterattack was defeated, the U.S. commanders completed preparations for a corps-level offensive to capture Munda, bringing in further reinforcements and supplies. A secondary landing had been undertaken closer to Munda, around Laiana, to shorten supply lines. Medical and logistic support was also improved utilizing the secondary landing beach that had been established around Laiana on 14 July.[27] During the lull that followed, U.S. forces undertook a series of patrols to gather information about Japanese dispositions; a number of minor firefights took place during this time, with only limited casualties.[43] Meanwhile, the Japanese commander, Sasaki, also resolved to renew the offensive. He ordered Tomonari to launch another counterattack on 25 July,[39] aiming an attack on the U.S. right flank around Horseshoe Hill and then rolling up the Allied line east along the Munda Trail. Griswold ordered a renewed offensive on 22 July; this began three days later and nullified the Japanese efforts.[44]

Supported by a strong naval bombardment on Lambeti Plantation, between Munda and Laiana, augmented by shore-based artillery and airstrikes, on 25 July the U.S. attack commenced with two divisions being committed across the front.[45] The 37th Division attacked towards Bibilo Hill while the 43rd Division drove towards Lambeti Plantation and the airfield.[46] After a sustained offensive that lasted two weeks, the Allies eventually captured the airfield in the Battle of Munda Point on 4–5 August. As the Japanese began withdrawing from New Georgia towards Kolombangara, U.S. forces undertook mopping up operations throughout August, during which time they advanced north from Munda to link up with the U.S. Marines and U.S. Army troops that had landed around Bairoko in early July. Bangaa Islet was secured in late August, while Arundel Island was captured later the following month.[47]

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