The 'Battle of Rennell Island' was fought between Japanese aircraft and US warships as the final major naval battle of the Guadalcanal campaign in the Solomon islands group (29/30 January 1943).

The battle was fought in the South Pacific waters between Rennell island and Guadalcanal in the southern part of the Solomon islands group. In the battle, Japanese land-based torpedo bombers, providing protection for the impending 'Ke' (i) evacuation of the surviving Japanese forces from Guadalcanal, made several attacks over two days on US warships operating as a task force to the south of Rennell island. In addition to approaching Guadalcanal with the objective of engaging any Japanese ships which appeared, the US task force was protecting an Allied transport ship convoy carrying replacement troops to Guadalcanal.

As a result of the Japanese air attacks on the task force, one US heavy cruiser was sunk, one destroyer was severely damaged, and the rest of the US task force was forced to retreat from the southern part of the Solomon islands group. Partly as a result of their success in the 'Battle of Rennell Island', the Japanese successfully evacuated their remaining troops from Guadalcanal by 7 February 1943, leaving it in the hands of the Allies and ending the battle for the island.

On 7 August 1942, Allied forces, comprising primarily US troops, landed on Guadalcanal, Tulagi and the Florida islands in the Solomon islands group in the course of the 'Watchtower' and 'Ringbolt' undertakings. The landings on the islands were meant to deny the Japanese their uses as bases from which to threaten the supply routes between the USA 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 on New Britain island while also supporting the Allied New Guinea campaign. The landings began the six-month Guadalcanal campaign.

The last major attempt by the Japanese to drive Allied forces from Guadalcanal and Tulagi was defeated during the decisive 'Naval Battle of Guadalcanal' early in November 1942. Thereafter, the Imperial Japanese navy was able to deliver only subsistence supplies and a few replacement troops to the Imperial Japanese army forces on Guadalcanal. Because of the threat from Allied aircraft based at Henderson Field on Guadalcanal, as well as the nearby presence of US aircraft carriers, the Japanese delivered these supplies at night, usually by destroyer or submarine, in operations which became known to the Allies as 'Tokyo Express' undertakings. These supplies and replacements were not sufficient to sustain the Japanese troops on the island, who by 7 December 1942, were losing about 50 men each day to malnutrition, disease and the combination of Allied ground and/or air attacks. On 12 December 1942, the Imperial Japanese navy proposed that Guadalcanal be abandoned. Despite initial opposition from army leaders, who still hoped that Guadalcanal could eventually be retaken, on 31 December 1942 the Imperial General Headquarters, with approval from Emperor Hirohito, agreed to evacuate all Japanese forces from the island and to establish a new line of defence for the Solomons on New Georgia island.

The evacuation was 'Ke' (i), which was scheduled to begin on 14 January 1943. An important element in the plan was an air superiority campaign to inhibit Allied aircraft and/or warships from disrupting the final stage of 'Ke' (i).

The Allies misinterpreted the preparations for 'Ke' (i) as the start of another Japanese offensive to attempt the recapture of Guadalcanal. At the same time, Admiral William F. Halsey, the Allied theatre commander, was under pressure from his superiors to complete the replacement of the 2^nd Marines, a regiment which had been in combat on Guadalcanal since August, with fresh US Army troops. Halsey hoped to take advantage of what he believed was an impending Japanese offensive to draw Japanese naval forces into battle, while at the same time delivering the replacement army troops to Guadalcanal. On 29 January, Halsey sent five task forces toward the southern part of the Solomons islands group to cover the relief convoy and to engage any Japanese naval forces that came within range. These five task forces included two fleet carriers, two escort carriers, three battleships, 12 cruisers and 25 destroyers.

Leading this array of task forces was Task Group 62.8, the troop convoy of four transports and four destroyers. Ahead of the troop convoy, between Rennell island and Guadalcanal, was Rear Admiral Robert C. Giffen’s Task Force 18, a close support group comprising the heavy cruisers Wichita (flag), Chicago and Louisville, the light cruisers Montpelier, Cleveland and Columbia, the escort carriers Chenango and Suwannee, and eight destroyers. A fleet carrier task force, centred on the carrier Enterprise, steamed about 250 miles (400 km) behind TG62.8 and TF18. The other fleet carrier and battleship task forces were about 150 miles (240 km) farther back. Giffen, with Wichita and the two escort carriers, had just arrived in the Pacific after participating in the Allied 'Torch' landing in French North-West Africa. Chicago had just arrived back in the South Pacific after the completion of repairs to the damage she had suffered during the 'Battle of Savo Island', almost six months earlier.

In addition to protecting the troop convoy, TF18 was charged with rendezvousing with a force of four US destroyers, stationed at Tulagi, at 21.00 on 29 January in order to conduct a sweep up 'The Slot' through New Georgia Sound to the north of Guadalcanal on the following day to screen the unloading of the troop transports at Guadalcanal. The escort carriers, under Commodore Ben Wyatt and steaming at 18 kt, were too slow to allow Giffen’s force to make the scheduled rendezvous, so Giffen left the carriers behind with two destroyers at 14.00 and pushed on ahead at 24 kt. Wary of the threat from Japanese submarines, which Allied intelligence indicated were probably in the area, Giffen arranged his cruisers and destroyers for anti-submarine defence as he was not expecting an air attack. The cruisers were disposed in two columns, spaced 2,500 yards (2285 m) apart, with Wichita, Chicago and Louisville, in that order, to starboard, and Montpelier, Cleveland and Columbia to port. The six destroyers were disposed in a semi-circular formation 2 miles (3.2 km) ahead of the cruiser columns.

Giffen’s force was tracked by Japanese submarines, which reported its location and movement. At about the middle of the afternoon, based on the submarine reports for Vice Admiral Jinichi Kusaka’s South-East Asia Fleet and 11^th Air Fleet, 16 Mitsubishi G4M 'Betty' twin-engined medium bombers of the 705^th Air Group and 16 Mitsubishi G3M 'Nell' twin-engined medium bombers of the 701^st Air Group, all armed with torpedoes rather than bombs, took off from Rabaul to locate and attack Giffen’s force. One G3M turned back with engine trouble, leaving the air attack force with 31 bombers. The leader of the 705^th Air Group's aircraft was Lieutenant Tomoo Nakamura, and Lieutenant Commander Joji Hagai commanded the aircraft of the 701^st Air Group.

At sunset, as TF18 steamed to the north-west at a position 50 miles (80 km) to the north of Rennell island and 160 miles (260 km) to the south of Guadalcanal, several of Giffen’s ships detected unidentified aircraft on radar 60 miles (97 km) to the west of their formation. Having previously insisted on absolute radio silence, Giffen gave no orders about what to do about the unidentified contacts, or in fact any orders at all. With the setting of the sun, TF18’s combat air patrol of fighters from the two escort carriers returned to their ships, leaving Giffen’s ships without air cover.

The radar contacts were the approaching Japanese torpedo bombers, which circled around to the south of TF18 so that they could attack from the east, with the black backdrop of the eastern sky behind them. From this direction, the Japanese bombers were hidden by the night sky, but Giffen’s ships were silhouetted against the twilight of the western horizon. The aircraft of the 705^th Air Group attacked first, beginning at 19.19. All of Nakamura’s aircraft missed with their torpedoes and one was shot down by anti-aircraft fire from Giffen’s ships.

Believing that the attack was over, Giffen ordered his ships to cease zigzagging and continue toward Guadalcanal on the same course and at the same speed. Meanwhile, a Japanese reconnaissance aeroplane began dropping flares and floatlights to mark TF18’s course and speed for the impending attack by Hagai’s bombers.

At 19.38, the 701^st Air Group attacked, hitting Chicago with two torpedoes, causing heavy damage and bringing the cruiser to a dead stop. Another torpedo hit Wichita but failed to detonate. Two bombers, including that of Hagai, were shot down by anti-aircraft fire. At 20.08, Giffen ordered his ships to reverse direction, to slow to 15 kt, and to cease fire. The absence of muzzle flashes concealed the ships from the Japanese aircraft, which had all departed the area by 23.35. In pitch darkness, Louisville managed to take the crippled Chicago in tow and slowly headed south, away from the battle area, escorted by the rest of TF18.

On being told of these events, Halsey immediately took steps to try to protect Chicago, notifying the escort carriers to make sure they had a combat air patrol in place at first light, ordering Enterprise's task force to approach and to augment the escort carriers' combat air patrol, and sending the fleet tug Navajo to take over the tow, a change which had been completed by 08.00. Between the break of day and 14.00, numerous Japanese reconnaissance aircraft approached TF 18. Although they were all chased away by the combat air patrol, they observed and reported Chicago's position. At 12.15, Lieutenant Commander Kazuo Nishioka led a force of 11 G4M torpedo bombers of the 751^st Air Group, based at Kavieng and staging through Buka, New Guinea, to attack the damaged US cruiser. An Australian coastwatcher in the Solomon islands group warned the US forces of the bombers and estimated their arrival time as 16.00. However, Halsey ordered the other cruisers to leave Chicago behind and head for Efate island in the New Hebrides islands group. They departed at 15.00, leaving behind six destroyers to protect Chicago and Navajo.

At 15.40, Enterprise was 43 miles (69 km) distant from Chicago, with 10 of her fighters constituting a combat air patrol over the damaged cruiser. At this time, four of the combat air patrol’s fighters chased and shot down a scouting G4M bomber. At 15.54, Enterprise's radar detected the incoming bombers and the carrier launched 10 more fighters. The escort carriers, however, had difficulties in getting their aircraft launched and the fighters did not attack the bombers until the engagement was over.

At first, the Japanese bombers appeared to be trying to approach and attack Enterprise, but then turned toward Chicago after six of Enterprise's fighters had started to engage them. Four other combat air patrol fighters chased the the 751^st Air Group's bombers as they entered the anti-aircraft fire from Chicago's escorting destroyers. Two of the bombers were shot down before they could release their torpedoes, and six more were shot down moments later, but not before they dropped their torpedoes.

One torpedo hit the destroyer La Vallette in her forward engine room, killing 22 men and causing heavy damage. Chicago was hit by four torpedoes, one forward of the bridge and three others in her engineering spaces. Captain Ralph O. Davis of Chicago ordered the ship to be abandoned, and she sank, stern first, 20 minutes later. Navajo and the escorting destroyers rescued 1,049 survivors, but 62 of her crew died. A final attack force of Japanese torpedo bombers failed to find the remaining US ships. Navajo took La Vallette in tow, and all of TF18’s remaining ships made port at Espiritu Santo island without further incident.

The Japanese publicised the results of the engagement widely, claiming to have sunk a battleship and three cruisers.On the other hand, the USA tried to conceal the loss of Chicago from the public for some time, with Admiral Chester W. Nimitz, commander-in-chief of the Pacific Fleet and the Pacific Ocean Areas, threatening to 'shoot' any of his staff who leaked the loss to the press. Halsey and Nimitz blamed Giffen for the defeat and noted this in Giffen’s official performance report for the period. The defeat and resulting recriminations did not affect the career of Giffen, who continued to lead Allied battleship and cruiser task forces in the Pacific until 1944, and was later promoted to vice admiral.

With Japanese aircraft engaged with TF18, the Allied transports completed their replacement of the remaining marines on Guadalcanal over the last two days of January. During this time, the other Allied task forces, including the two fleet carrier task forces, took station in the Coral Sea in anticipation of an expected Japanese offensive in the southern part of the Solomon islands group.

With TF18 forced to retreat, very few Allied naval forces were left in the immediate area of Guadalcanal, allowing the Japanese to retrieve most of their remaining ground forces from Guadalcanal over three nights between 2 and 7 February. The Allies were not aware of the Japanese withdrawal until it was over, but the evacuation of 11,000 starving troops and the loss of one cruiser became a footnote to the securing of Henderson Field and Guadalcanal, which provided the air support springboard to successfully complete the Solomon islands campaign, a major turning point in the Pacific War.