The 'Battle of Empress Augusta Bay', sometimes known as the 'Battle of Gazelle Bay', was fought between Japanese and US naval forces in the area of Empress Augusta Bay on Bougainville in the Solomon islands group within the context of the US 'Cherryblossom' invasion of that island (1/2 November 1943).

The battle may also be considered as part of the linked campaigns for the Solomon islands group and New Guinea, and was significant as part of a broader Allied strategy, known as 'Cartwheel' aimed at the isolation of major Japanese base at Rabaul on New Britain island: the intention was to establish a beach-head on Bougainville, within which an airfield would be built.

The naval battle took place at the end of the first day of the landings around Cape Torokina after the Japanese had sortied a large force from Rabaul in an effort to replicate the success they had achieved at Savo island in August 1942 in response to Allied amphibious landings in the south-eastern part of the Solomon islands group. Ultimately, the covering force of US warships was able to turn back the Japanese force and the landings around Cape Torokina were successful.

On 1 November 1943, Major General Allen H. Tunage’s 3^rd Marine Division landed at Cape Torokina in Empress Augusta Bay, which was known to the Japanese as Gazelle Bay. Following the Allied successes in the more south-eastern parts of the Solomon islands campaign, the landings were undertaken as part of an Allied plan to establish a number of air bases in the region in order to project air power towards the Japanese stronghold around Rabaul, whose isolation and reduction were a key part of 'Cartwheel'. Empress Augusta Bay had been selected for the US landing as it was at the outer limit of the range of Allied fighter aircraft coverage, and as Lieutenant General Harukichi Hyakutake’s numerically superior 17^th Army was concentrated at other, more strategic sites in the island’s north and south. The marine assault was backed by Rear Admiral Aaron S. Merrill’s Task Force 39, which comprised cruisers and destroyers. TF39 was tasked with covering he vulnerable transports and minelayers from air attack and from attack from the sea.

The Japanese responded with air attacks and a powerful naval force from Rabaul under the command of Rear Admiral Sentaro Omori. The Japanese formation was hastily assembled from whatever ships were on hand, many of which had not trained or fought together before this time. Omori’s force comprised the heavy cruisers Myoko and Haguro, the light cruisers Agano and Sendai, and the destroyers Naganami, Hatsukaze, Wakatsuki, Shigure, Samidare and Shiratsuyu. These warships were organised into Cruiser Division 5, which contained the two heavy cruisers and two screens (left and right) each comprising one light cruiser and three destroyers. The left screen was commanded by Rear Admiral Matsuji Ijuin, while the right was under the command of Rear Admiral Morikazu Osugi. Initially, this force had included five destroyer transports laden with troops for a counter-landing, but following several delays, the decision was made for the transports to return to Rabaul, whence it would sortie later to land its troops around Koromokina Lagoon on 7/8 November.

Ranged against the Japanese force was TF39 centred on Cruiser Division 12 with the cruisers Montpelier, Cleveland, Columbia and Denver. These four 'Cleveland' ships were officially categorised as light cruisers, but were nearly the size of the Japanese heavy cruisers and each armed with 12 radar-aimed 6-in (152.4-mm) rapid-fire guns. TF39 also included Destroyer Squadron 23 comprising two destroyer divisions: Destroyer Division 45 comprised Charles Ausburne, Dyson, Stanly, Claxton, and Destroyer Division 46 Spence, Thatcher, Converse and Foote. Merrill was in overall command of the TF39 and also directly controlled Cruiser Division 12, while Captain Arleigh A. Burke commanded Destroyer Division 45 and Commander Bernard L. Austin Destroyer Division 46.

As the Japanese ships sortied toward Cape Torokina, the Americans were already in the process of withdrawing most of their landing craft and troop transports from the area and assembling them to the south-west of Empress Augusta Bay. The 12 transport vessels were ordered to depart at about 18.00, while four cargo vessels, still only partially unloaded, remained in the landing area. The US minelayers operating off Cape Moltke were also withdrawn. Meanwhile, US reconnaissance aircraft had detected Omori’s force, and in response Merrill’s force, which had been shelling Japanese positions around Buka in northern Bougainville on the previous day, began steaming to the north from around Vella Lavella island to effect an interception, departing before 00.00 on 1/2 November. The US ships then established themselves to block the entrance to Empress Augusta Bay. The Japanese approached from the north-west, aiming to bombard the invasion force in their transports and on the shore. At 01.30 on 2 November, Haguro was struck amidships by a US air attack, the resulting damage necessitating a significant reduction in speed for the entire Japanese formation.

The US ships gained radar contact at 02.27 on 2 November, and Merrill deployed his force into three columns, sending Burke’s destroyers to attack the Japanese northern flank, while the cruisers turned about to remain out of torpedo range, with the remaining destroyers from Austin’s group tasked with launching a torpedo attack on the southern flank. From the leading position in the US formation, Burke sent the four destroyers of Destroyer Division 45 forward for a torpedo attack and at 02.46 fired a salvo toward the Japanese. Around the same time, Sendai's division fired eight torpedoes. Each attack was detected and each group manoeuvred away from the opposition’s torpedoes. In the resulting confusion, the Japanese force became separated into three groups.

Merrill then ordered Destroyer Division 46 to attack. The unprepared Foote misinterpreted the command and became separated from the other ships. Despite her captain’s best efforts, Foote was unable to rejoin the fight and was in some danger of colliding with other friendly ships. At about 02.50, after it had become apparent that Destroyer Division 45’s torpedo attack had failed to achieve complete surprise, the US cruisers opened fire, quickly disabling Sendai, whose rudder became jammed.

After firing her torpedoes, Samidare collided with Shiratsuyu, and both ships were subsequently forced to retire from the battle, Samidare receiving 5-in (127-mm) hits at 03.00. Myoko also collided with Hatsukaze, slicing off her bow. Myoko also sustained significant damage in this collision. Meanwhile, Haguro was hit by several cruisers with 6-in (152.4-mm) shells, of which a few detonated. Relying on visual tracking of their targets, and then only with difficulty, the Japanese cruisers pinpointed the US cruisers and opened fire at 03.13. At 03.20 the ships of Cruiser Squadron 12 fired several torpedoes at Cruiser Division 12. At 02.27 numerous hits on the ships of Cruiser Division 12 were erroneously reported to Omori, but all had in fact missed their targets.

The Americans were also having problems as Spence and Thatcher also collided but were able to continue in the battle. Foote was struck by a torpedo which blew off her stern, leaving 19 men dead and 17 wounded. The drifting Foote subsequently became a navigational hazard to the other ships, which added further to the battle’s confusion. Foote was busy for the remainder of the engagement trying to remain afloat and fighting off a Japanese air attack. Without fire-control radar, the Japanese depended heavily on flares to illuminate their targets. Cruiser Division 12 repeatedly manoeuvred to avoid the light of starshells fired by the opposing ships, but was finally illuminated by brilliant flares dropped by Japanese spotter aircraft.

Between 03.20 and 03.25 Denver received three 8-in (203.2-mm) shells, which failed to detonate. Also, while closing with a group of Japanese destroyers in the center, Spence was hit on the waterline by a shell that also failed to detonate. At this point the Japanese fire was heavy and increasingly accurate, and in response the US cruisers began to manoeuvre behind a smokescreen, which successfully interfered with the Japanese gunnery.

Throughout the battle the US destroyers experienced difficulty maintaining contact with each other, and several times came close to firing on friendly ships, underscoring the difficulty in fighting night actions even when equipped with radar and IFF systems. A later evaluation of the battle revealed that Destroyer Division 46 missed an opportunity to torpedo the central group of Japanese ships because of uncertain identification, and then turned to the north and concentrated fire on Sendai.

By 03.37, believing that he had sunk a heavy cruiser and worried about being caught in daylight by US carrierborne aircraft, Omori ordered a retreat. Merrill’s cruisers closed to bombard the Japanese forces withdrawing to the west, engaging Hatsukaze at a range of more than 17,500 yards (16000 m), but were unable to score any hits.

At about 04.00, Destroyer Divisions 45 and 46 engaged in a confused mêlée with retreating Japanese stragglers, sinking Sendai and driving off the remaining warships of the northern group. Just before 04.13 Spence lost speed as a result of water in a fuel line and fell out of formation. The US ships reported many hits on the Japanese radar contacts. Destroyer Division 45 fired on the limping Spence in error, causing no damage. Cruiser Division 12 and Spence engaged a Japanese straggler at 05.10. Unable to distinguish between the straggler and Spence, the cruisers ceased fire. By 05.19, Destroyer Division 45 came to the aid of Spence, which by this time had almost exhausted her ammunition. The Japanese straggler, the heavily damaged Hatsukaze, exploded and sank.

At the break of day, Merrill ordered the pursuit to be brought to an end and all ships, many low on fuel and ammunition, to make rendezvous with the hapless Foote, as Merrill was concerned about the possibility of his ships being exposed to air attack. This proved prescient, as a heavy Japanese air attack, comprising more than 100 aircraft, had been launched from Rabaul early in the morning to attack the US ships which had converged around Foote. This Japanese attack was fought off with assistance from land-based US and New Zealand aircraft, with heavy losses inflicted on the attacking aircraft. The Japanese ships scored two hits on Montpelier, whose crew suffered nine men wounded. Foote was subsequently towed to Tulagi island for repairs.

The 'Battle of Empress Augusta Bay' thus came to an end as a complete victory for the US naval force. The US attack had not only deflected the Japanese from the vulnerable transport ships and landing craft around Cape Torokina, but had also inflicted significant damage on their opponents. For the loss of just 19 men killed and 26 wounded, and three ships damaged, the US ships had sunk one light cruiser and one destroyer, and damaged two cruisers and two destroyers. Japanese casualties have been reported as being between 198 and 658 men killed. As many as 25 Japanese aircraft had also been shot down in the air attack following the naval action. The Japanese subsequently sent a submarine to locate survivors: none were found from Hatsukaze, but some of Sendai's survivors were rescued.

In the aftermath, the Japanese ships returned to Rabaul, where they were joined by four cruisers and more destroyers from Truk in the Caroline islands group for another attack on the Allied landing forces at Bougainville. On 5 November, however, two US aircraft carriers raided Rabaul, heavily damaging four heavy cruisers, which had to withdraw to Truk. This ended the Japanese warship threat to the Allied landing forces at Bougainville. Omori was later relieved of his command as a result of the failed action. US ground forces soon secured their beach-head around Cape Torokina and the perimeter was subsequently expanded into a substantial lodgement. A PT-boat base was established on Puruata island and several air bases were built within the Cape Torokina perimeter. These bases were subsequently employed in the reduction of Rabaul. By the start of February 1944, the US forces had built up a force of more than 400 aircraft on Bougainville, and before the end of that month the Japanese air defences around Rabaul had been defeated. On the ground, throughout the remainder of 1943 the US Marines and Japanese fought several minor land battles around the perimeter, culminating during March 1944 in a major Japanese counterattack, which was defeated with Japanese heavy losses.