Operation Battle of the Coral Sea

The 'Battle of the Coral Sea' was a naval battle with strategic implications between the Imperial Japanese navy and the naval and air forces of the USA and Australia (4/8 May 1943).

Taking place in the Coral Sea, a marginal sea of the South Pacific Ocean off the north-eastern coast of Australia and to the south of the Solomon islands group, the battle is historically significant as the first action in which the opposing fleets neither sighted nor fired upon one another, instead attacking over the horizon with carrierborne aircraft.

To strengthen their defensive position in the South Pacific, the Imperial Japanese headquarters decided that Port Moresby, the main town of the Papua region of the island of New Guinea and a major Allied base area, together with the island of Tulagi in the Solomon islands group, had to be taken in amphibious undertakings. The 'Mo' (ii) plan to take Port Moresby involved several major elements of Admiral Isoroku Yamamoto’s Combined Fleet. Two fleet carriers and one light carrier were assigned to provide air cover for the invasion force, under the overall command of Vice Admiral Shigeyoshi Inoue. The USA learned of the Japanese plan through signals intelligence, and sent two US Navy carrier task forces and a joint US and Australian cruiser force to oppose the offensive, under the overall command of US Rear Admiral Frank J. Fletcher.

On 3/4 May, Japanese forces invaded and occupied Tulagi, although several supporting warships were sunk or damaged in a surprise attack by aircraft of the US fleet carrier Yorktown. Thus alerted to the presence in the area of at least one US aircraft carrier, the Japanese fleet carriers advanced toward the Coral Sea to locate and destroy the Allied naval forces. On the evening of 6 May, the two carrier fleets closed to within 80 miles (130 km) of each other, but neither detected the other in the darkness. On the following day, both fleets launched air attacks against what they thought was the opposing fleet’s aircraft carriers, but both sides actually attacked other targets. The USA sank the Japanese light carrier Shoho and the Japanese sank a US destroyer and damaged the fleet oiler Neosho. On 8 May, both sides finally located and attacked the other’s fleet carriers: the Japanese fleet carrier Shokaku was damaged, and the US fleet carrier Lexington was critically damaged and later scuttled, while the fleet carrier Yorktown was slightly damaged.

Having suffered heavy aircraft losses and carriers sunk or damaged, the two forces disengaged and retired from the area. Because of the loss of carrier air cover, Inoue also recalled the Port Moresby invasion force. Although the battle was a tactical victory for the Japanese in terms of ships sunk, it has been described as a strategic victory for the Allies: the battle was the first occasion since the start of the war that a major Japanese advance had been turned back and, more importantly, the damage to Shokaku and the aircraft losses of Zuikaku prevented both ships from participating in the decisive 'Battle of Midway' resulting from the Japanese 'Mi' (ii) undertaking in the course of the following month.

On 8 December 1941 (7 December US time), Japan declared war on the USA and the British empire, after Japanese forces attacked Malaya, Singapore and Hong Kong as well as the US naval base at Pearl Harbor in the Hawaiian islands group. In launching this war, Japanese leaders sought to neutralise the US Pacific Fleet, seize territory rich in natural resources, and obtain strategic military bases for the defence of their far-flung empire. In the words of the Combined Fleet's 'Secret Order Number One' of 1 November 1941, the goals of the initial Japanese campaigns in the impending war were to '[eject] British and American strength from the Netherlands Indies and the Philippines, [and] to establish a policy of autonomous self-sufficiency and economic independence'.

To support these goals, during the first few months of 1942, the Japanese forces attacked Malaya and also seized control of the Philippine islands group, Singapore, the Netherlands East Indies, the island of Wake, New Britain, New Ireland the Gilbert islands group and Guam in the Mariana islands group, inflicting heavy losses on opposing Allied land, naval and air forces. As noted above, the Japanese planned to exploit the natural resources of these areas and also use the conquered territories for the creation of a strategic defensive perimeter from which it expected to employ attritional tactics to defeat or exhaust any Allied counter-offensive.

Shortly after the war began, the general staff of the Imperial Japanese navy recommended an invasion of northern Australia to prevent Australia from being used as a base from which the Allies could threaten Japan’s perimeter defences in the South Pacific. The Imperial Japanese army rejected the recommendation, stating that it did not have the forces or shipping capacity available to conduct such an operation. At the same time, Vice Admiral Shigeyoshi Inoue, commander of the 4th Fleet (also called the South Seas Force), which comprised most of the naval units in the South Pacific area, advocated the occupation of Tulagi in the south-eastern sector of the Solomon islands group and Port Moresby in New Guinea, which would put northern Australia within range of Japanese land-based aircraft. Inoue believed the capture and control of these locations would provide greater security and defensive depth for the major Japanese base at Rabaul on New Britain. The navy’s general staff and the army both accepted Inoue’s proposal and promoted further operations, using these locations as supporting bases, to seize New Caledonia, Fiji and Samoa, and thereby cut the maritime lines of supply and communication between Australia and the USA.

In April 1942, the army and navy developed the 'Mo' (ii) plan, which called for Port Moresby to be invaded from the sea and secured by 10 May. The plan also included the prior seizure of Tulagi island on 2/3 May for the navy to establish a seaplane base for potential air operations against Allied territories and forces in the South Pacific and to provide a base for reconnaissance aircraft. Upon the completion of 'Mo' (ii), the navy planned to initiate 'Ry', using ships released from 'Mo' (ii), to seize Nauru and Ocean islands for their phosphate deposits on 15 May. Another operation, 'Fs', were to be planned for the seizure of Fiji, Samoa and New Caledonia once 'Mo' (ii) and 'Ry' had been completed. Because of a damaging air attack by Allied land- and carrier-based aircraft on Japanese naval forces invading the area of Lae and Salamaua area in New Guinea during March, Inoue requested that the Combined Fleet send carriers to provide air cover for 'Mo' (ii). Inoue was especially worried about Allied bombers stationed at the Townsville and Cooktown air bases in Australia, which lay beyond the range of his own land-based bombers based at Rabaul and Lae.

Commander of the Combined Fleet, Yamamoto was concurrently planning an operation for June that he hoped would lure the Pacific Fleet’s carriers, none of which had been damaged in 'Ai', into a decisive showdown in the central Pacific near Midway atoll. In the meantime Yamamoto detached some of his large warships, including two fleet carriers, one light carrier, one cruiser division, and two destroyer divisions, to support 'Mo' (ii), and placed Inoue in command of the naval portion of the operation.

Unknown to the Japanese, the US Navy, led by the Communication Security Section of the Office of Naval Communications, had for several years enjoyed increasing success with penetrating Japanese communication ciphers and codes. By March 1942, the USA was able to decipher up to 15% of the Japanese navy’s 'Ro' or 'Naval Codebook D' code (called 'JN-25B' by the USA), which the navy used for about half of its communications. By the end of April, the USA was able to read as much as 85% of the signals broadcast in the 'Ro' code. In March 1942, the USA first noted mention of the 'Mo'(ii) operation in intercepted messages. On 5 April, the USA intercepted a Japanese naval message directing a carrier and other large warships to proceed to Inoue’s area of operations. On 13 April, the British deciphered a Japanese naval message informing Inoue that the 5th Carrier Division, comprising the fleet carriers Shokaku and Zuikaku, was on its way to Inouye’s command from Formosa via the main Japanese naval base at Truk in the Caroline islands group. The British passed the message to the USA, along with their conclusion that Port Moresby was the likely target of 'Mo' (ii).

Admiral Chester W. Nimitz, commander of the US forces in the Pacific Ocean Areas, and his staff discussed the deciphered messages and agreed that the Japanese were likely initiating a major operation in the South-West Pacific Area during the early part of May with Port Moresby as the probable target. The Allies regarded Port Moresby as a key base for a planned counter-offensive, under the command of General Douglas MacArthur, against Japanese forces in the South-West Pacific Area. Nimitz’s staff also concluded that the Japanese operation might include carrier raids on Allied bases in Samoa and at Suva in the Fijian islands group. After consultation with Admiral Ernest J. King, commander-in-chief of the US Fleet, Nimitz decided to contest the Japanese operation by sending all four of the Pacific Fleet’s available aircraft carriers to the Coral Sea. By 27 April, further signals intelligence had confirmed most of the details and targets of the 'Mo' (ii) and 'Ry' plans.

It was on 29 April that Nimitz issued orders that sent his four carriers and their supporting warships toward the Coral Sea. Task Force 17, commanded by Fletcher and comprising the fleet carrier Yorktown, escorted by three cruisers and four destroyers and supported by a replenishment group of two oilers and two destroyers, was already in the Tonga islands group in the South Pacific, having departed Tongatabu on 27 April en route to the Coral Sea. TF11, commanded by Rear Admiral Aubrey W. Fitch and comprising the fleet carrier Lexington with two cruisers and five destroyers, was between Fiji and New Caledonia. TF16, commanded by Vice Admiral William F. Halsey and including the fleet carriers Enterprise and Hornet, had just returned to Pearl Harbor from the 'Doolittle Raid' in the central Pacific. TF16 immediately departed but would not reach the South Pacific in time to participate in the battle. Nimitz placed Fletcher in command of the Allied naval forces in the South Pacific area until Halsey arrived with TF16. Although the Coral Sea area fell into MacArthur’s area of command, Fletcher and Halsey were directed to continue to report to Nimitz rather than MacArthur while in the Coral Sea.

Based on interceptions of unencrypted radio traffic from TF16 as it returned to Pearl Harbor, the Japanese assumed that all but one of the US Navy’s carriers were in the central Pacific. The Japanese did not know the location of the remaining carrier, but did not expect any US carrier response to 'Mo' (ii) until the operation was well under way.

Late in April, the Japanese submarines Ro-33 and Ro-34 reconnoitered the area where landings were planned. The submarines investigated Rossel Island and the Deboyne group anchorage in the Louisiade Archipelago, the Jomard Channel, and the route to Port Moresby from the east. They did not sight any Allied ships in the area and returned to Rabaul on 23 and 24 April respectively.

The Port Moresby Invasion Force, commanded by Rear Admiral Koso Abe, included 11 transport ships carrying about 5,000 soldiers of the army’s South Seas Detachment and about 500 naval troops of the 3rd Kure Special Naval Landing Force. Escorting the transports was the Port Moresby Attack Force with the light cruiser Yubari and six relatively old 'Kamikaze' and 'Mutsuki' class destroyers under the command of Rear Admiral Sadamichi Kajioka. Abe’s ships departed Rabaul for the 970-mile (1560-km) passage to Port Moresby on 4 May and were joined by Kajioka’s force on the following day. Steaming at 8 kt, the ships planned to transit the Jomard Channel in the Louisiade islands group to pass around the southern tip of New Guinea and arrive off Port Moresby by 10 May. At this time, the Allied garrison at Port Moresby numbered about 5,333 men, but only half of these were infantry and all were badly equipped and undertrained.

Leading the invasion of Tulagi was the Tulagi Invasion Force under the command of Rear Admiral Kiyohide Shima and comprising two minelayers, two older 'Mutsuki' class destroyers, five minesweepers, two submarine chasers and one transport vessel carrying about 400 men of the 3rd Kure Special Naval Landing Force. In support was the Close Support Force with the light carrier Shoho and the destroyers Sazanami, and the Support Force, Main Body with the heavy cruisers Aoba, Kako, Kinugasa and Furutaka: both the Close Support Force and the Support Force, Main Body were commanded by Rear Admiral Aritomo Goto. A separate Close Cover Force, commanded by Rear Admiral Kuninori Marumo, comprised the light cruisers Tenryu and Tatsuta, the seaplane tender Kamikawa Maru and three gunboats, joined the Close Support Force in the provision of distant protection for the Tulagi invasion. Once Tulagi had been secured on 3 or 4 May, the Close Support Force and Close Cover Force were to reposition themselves to help screen the Port Moresby invasion. Inoue supervised the 'Mo' (ii) operation from the light cruiser Kashima, with which he arrived at Rabaul from Truk on 4 May.

Goto’s force departed Truk on 28 April, passed through the Solomon islands group between Bougainville and Choiseul islands, and took station near New Georgia island. Marumo’s Close Support Force sortied from New Ireland on 29 April and headed for Thousand Ships Bay on Santa Isabel island to establish a seaplane base on 2 May in support of the assault on Tulagi. Shima’s Tulagi Invasion Force departed Rabaul on 30 April.

The Carrier Strike Force, with the fleet carriers Zuikaku and Shokaku, the heavy cruisers Myoko and Haguro, and the destroyers Ariake, Yugure, Shigure, Shiratsuyu, Ushio and Akebono, sortied from Truk on 1 May under the command of Vice Admiral Takeo Takagi flying his flag on Myoko, with Rear Admiral Chuichi Hara, on Zuikaku, in tactical command of the carrier air forces. The Carrier Strike Force was to proceed down the eastern side of the Solomon islands group and enter the Coral Sea in the area to the south of the island of Guadalcanal. Once in the Coral Sea, the carriers were to provide air cover for the invasion forces, eliminate Allied air power at Port Moresby, and intercept and destroy any Allied naval forces which entered the Coral Sea.

On their way to the Coral Sea, Takagi’s carriers were to deliver nine Mitsubishi A6M Reisen 'Zero' single-engined fighters to Rabaul. Adverse weather during two attempts to make the delivery on 2/3 May compelled the aircraft to return to the carriers, stationed 280 miles (440 km) from Rabaul, and one of the fighters was forced to ditch in the sea. In order to try to maintain the 'Mo' (ii) timetable, Takagi was had to abandon the delivery mission after the second attempt and direct his force toward the Solomon islands group to refuel.

To provide advance warning of the approach of any Allied naval forces, the Japanese sent the submarines I-22, I-24, I-28 and I-29 as a scouting line about 520 miles (830 km) to the south-west of Guadalcanal. Fletcher’s forces had entered the Coral Sea area before the submarines took station, however, and the Japanese were therefore unaware of their presence. Another submarine, I-21, which had been despatched to scout around Nouméa on New Caledonia island, was attacked by aircraft from Yorktown on 2 May. The submarine suffered no damage and apparently did not realise that it had been attacked by carrierborne aircraft. Ro-33 and Ro-34 were also deployed in an attempt to blockade Port Moresby, arriving off the town on 5 May, but neither of these boats engaged any ships during the battle.

On the morning of 1 May, TF17 and TF11 united about 350 miles (560 km) to the north-west of New Caledonia, and Fletcher immediately detached TF11 to refuel from the oiler Tippecanoe while TF17 refuelled from Neosho. TF17 completed refuelling on the following day, but TF11 reported that its ships would not have completed refuelling until 4 May. Fletcher elected to take TF17 to the north-west toward the Louisiade islands group and ordered TF11 to meet TF44, which was en route from Sydney and Nouméa, on 4 May once refuelling had been completed. TF44 was a joint Australia and US force under MacArthur’s command, led by a British officer on loan to the Australian navy, Rear Admiral J. G. Crace, and comprising the Australian heavy cruisers Australia and Hobart and the US heavy cruiser Chicago, together with three destroyers. Once it completed refuelling TF11, Tippecanoe departed the Coral Sea to deliver its remaining fuel to Allied ships at Efate in the New Hebrides islands group.

Early on 3 May, Shima’s force arrived off Tulagi and began disembarking the naval troops to occupy the island. Tulagi was undefended: the small garrison of Australian commandos and a Royal Australian Air Force reconnaissance unit had been evacuated just before Shima’s arrival. The Japanese forces immediately began work on the construction of a seaplane and communications base. Aircraft from Shoho covered the landings until a time early in the afternoon, when Goto’s force turned toward Bougainville to refuel in preparation to support the landings at Port Moresby.

At 17.00 on 3 May, Fletcher was notified that the Japanese invasion force for Tulagi had been sighted on the previous day as it approached the south-eastern end of the Solomon islands group. Unknown to Fletcher, TF11 completed refuelling that morning ahead of schedule and was only 69 miles (110 km) to the east of TF17, but was unable to communicate its status because of Fletcher’s orders to maintain radio silence. TF17 changed course and proceeded at 27 kt toward Guadalcanal to launch air attacks on the Japanese forces at Tulagi during the next morning.

On 4 May, from a position 120 miles (190 km) to the south of Guadalcanal, a total of 60 aircraft from TF17 flew three consecutive attacks on Shima’s forces off Tulagi. Yorktown's aircraft surprised Shima’s ships and sank the destroyer Kikuzuki and three of the minesweepers, damaged four other ships, and destroyed four seaplanes which were supporting the landings. The US force lost one torpedo bomber and two fighters in the attacks, but all of the aircrew were eventually rescued. After recovering its aircraft late in the evening of 4 May, TF17 retired to the south. In spite of the damage suffered in the carrier attacks, the Japanese continued construction of the seaplane base and had started to fly reconnaissance missions from Tulagi by 6 May.

Takagi’s Carrier Strike Force was refuelling 400 miles (645 km) to the north of Tulagi when it received word of Fletcher’s attack on 4 May. Takagi terminated the refuelling, headed to the south-east, and sent reconnaissance aircraft to search east of the Solomon islands group in the belief that the US carriers were in that area. There were no Allied ships in that area, and the reconnaissance aircraft therefore found nothing.

At 08.16 on 5 May, TF17 rendezvoused with TF11 and TF44 at a predetermined point 370 miles (595 km) to the south of Guadalcanal. At about the same time, four Grumman F4F Wildcat single-engined fighters from Yorktown intercepted a Kawanishi H6K 'Mavis' four-engined reconnaissance flying boat of the Yokohama Air Group of the 25th Air Flotilla based in the Shortland islands group and shot it down 13 miles (21 km) from TF11. The flying boat sent no report before it crashed, but when it failed to return to base the Japanese came to the correct assumption that it had been shot down by carrierborne aircraft.

A signal from Pearl Harbor notified Fletcher that radio intelligence had deduced that the Japanese planned to land their troops at Port Moresby on 10 May and that their fleet carriers would probably be operating close to the invasion convoy. Armed with this information, Fletcher directed TF17 to refuel from Neosho. After the refuelling had been completed on 6 May, Fletcher planned to take his force to the north in the direction of the Louisiade islands group and do battle on 7 May.

In the meantime, Takagi’s Carrier Strike Force steamed down the eastern side of the Solomon islands group throughout the day on 5 May, turned west to pass to the south of San Cristobal island, and entered the Coral Sea after transiting between Guadalcanal and Rennell island in the early morning hours of 6 May. Takagi started to refuel his ships 210 miles (340 km) to the west of Tulagi in preparation for the carrier battle he expected on the following day.

On 6 May, Fletcher absorbed TF11 and TF44 into TF17 and, believing that the Japanese carriers were still well to the north near Bougainville, continued to refuel. Reconnaissance sorties by aircraft from the US carriers throughout the day failed to locate any of the Japanese naval forces as these latter were just beyond scouting range.

At 10.00, a Kawanishi reconnaissance flying boat from Tulagi sighted TF17 and notified its headquarters: Takagi received the report at 10.50. At that time, Takagi’s force was about 345 miles (555 km) to the north of Fletcher’s task force, near the maximum range for his carrierborne aircraft. Takagi, whose ships were still refuelling, was not yet ready to engage in battle and concluded, based on the sighting report, that TF17 was heading to the south and increasing the range. Furthermore, Fletcher’s ships were under a large, low-hanging overcast which Takagi and Hara felt would make it difficult for their aircraft to find the US carriers. Takagi detached his two carriers with two destroyers under Hara’s command to head towards TF17 at 20 kt in order to be in position to attack at first light on the following day while the rest of his ships completed their refuelling.

USAAF Boeing B-17 Flying Fortress four-engined heavy bombers based in Australia and staging through Port Moresby attacked the approaching Japanese invasion forces, including Goto’s warships, several times during 6 May, but without success. MacArthur’s headquarters radioed Fletcher with reports of the attacks and the locations of the Japanese invasion forces. The reports of MacArthur’s aircrews of sighting a carrier, in fact Shoho, about 490 miles (790 km) to the north-west of TF17 further convinced Fletcher that fleet carriers were accompanying the invasion forces.

At 18.00, TF17 completed fuelling and Fletcher detached Neosho with the destroyer Sims to take station farther to the south at a prearranged rendezvous. TF17 then turned to head to the north-west in the direction of Rossel island in the Louisiade islands group. Unknown to the two adversaries, their carriers were only about 80 miles (130 km) distant from each other by 20.00 that night. At 20.00, Hara reversed course to meet Takagi, whose ships had completed refuelling and were now heading in Hara’s direction.

Late on 6 May or early on 7 May, Kamikawa Maru set up a seaplane base in the Deboyne islands group in order to help provide air support for the invasion forces as they approached Port Moresby. The rest of Marumo’s Close Cover Force then took station near the D’Entrecasteaux islands group to help screen Abe’s oncoming Transport Force convoy.

At 06.25 on 7 May, TF17 was 132 miles (213 km) to the south of Rossel island, and at this time, Fletcher sent Crace’s cruiser force, now designated Task Group 17.3, to block the Jomard Passage. Fletcher understood that Crace would be operating without air cover since TF17’s carriers would be busy trying to locate and attack the Japanese carriers. Although he appreciated that the detachment of Crace’s cruisers reduced the anti-aircraft defences for his carriers, Fletcher nonetheless decided the risk was necessary to ensure the Japanese invasion forces could not slip through to Port Moresby while he engaged the carriers.

Believing Takagi’s carrier force was somewhere to the north of him, in the vicinity of the Louisiade islands group, from 06.19 Fletcher directed Yorktown to send 10 Douglas SBD Dauntless single-engined dive-bombers as scouts to search that area. Hara in turn believed Fletcher was to the south of him and advised Takagi to send aircraft to search that area. About 350 miles (565 km) to the east of Fletcher, Takagi launched 12 Nakajima B5N 'Kate' single-engined torpedo bombers at 06.00 to scout for TF17. At about the same time, Goto’s cruisers Kinugasa and Furutaka launched four Kawanishi E7K2 single-engined biplane floatplanes to search an area to the south-east of the Louisiade islands group. Augmenting their search were several floatplanes from Deboyne, four H6K 'boats from Tulagi, and three Mitsubishi G4M 'Betty' twin-engined medium bombers from Rabaul. Each side readied the rest of its carrier attack aircraft for immediate launch once targets had been located.

At 07.22 one of Takagi’s carrier scouts, from Shokaku, reported US ships bearing 182° at a distance of 188 miles (303 km) from Takagi. At 07.45, the scout confirmed that it had located 'one carrier, one cruiser and three destroyers'. Another scouting aeroplane from Shokaku quickly confirmed the sighting. Shokaku's aircraft had actually sighted and misidentified the oiler Neosho and destroyer Sims, which as noted above had earlier been detached from the fleet to a southern rendezvous point. Believing that his aircraft had located the US carriers, Hara, with Takagi’s concurrence, immediately launched all his available aircraft. A total of 78 aircraft (18 A6M fighters, 36 D3A dive-bombers and 24 B5N torpedo-bombers) began to take off from Shokaku and Zuikaku at 08.00, and by 08.15 the entire attack package was on its way toward the reported sighting. The attack force was led by Lieutenant Commander Kakuichi Takahashi, with Lieutenant Commander Shigekazu Shimazaki leading its torpedo bombers.

At 08.20, one of Furutaka's floatplanes found Fletcher’s carriers and immediately reported it to Inoue’s headquarters at Rabaul, which passed the report on to Takagi. The sighting was confirmed by a floatplane from Kinugasa at 08.30. Takagi and Hara, confused by the conflicting sighting reports they were receiving, decided to continue with the strike on the ships to their south, but turned their carriers to the north-west to close the distance with Furutaka's reported contact. Takagi and Hara considered that the conflicting reports might mean that the US carrier force was operating in two separate groups.

At 08.15, an SBD from Yorktown sighted Goto’s force screening the invasion convoy. Making an error in his coded message, the pilot reported the sighting as 'two carriers and four heavy cruisers' 259 miles (417 km) to the north-west of TF17. Fletcher concluded that the Japanese main carrier force had been located and ordered the launch of all available aircraft to attack. By 10.13, the US attack package of 93 aircraft (18 F4F fighters, 53 SBD dive-bombers and 22 Douglas TBD Devastator single-engined torpedo bombers) was on its way. At 10.19, the pilot of the initial sighting aeroplane landed and discovered his coding error. Although Goto’s force included the light carrier Shoho, the pilot thought that he saw two cruisers and four destroyers and had thus sighted the main fleet. At 10.12, Fletcher received a report of one aircraft carrier, 10 transport vessels and 16 warships 35 miles (56 km) to the south of the initial sighting position. The B-17 heavy bombers actually saw the same thing as the carrier pilot: Shoho, Goto’s cruisers and the Port Moresby Invasion Force. Believing that the B-17s' sighting was the main Japanese carrier force, which was in fact well to the east, Fletcher directed the airborne attack force toward this target.

At 09.15, Takahashi’s attack force reached its target area, sighted Neosho and Sims, and for a period of about two hours searched vainly for the US carriers. Finally, at 10.51 the crews of Shokaku's scouting aircraft realised that they had been mistaken in their identification of the oiler and destroyer as aircraft carriers. Takagi now appreciated that the US carriers were between him and the invasion convoy, placing the invasion forces at great risk. At 11.15, the torpedo-bombers and fighters abandoned the mission and headed back toward the carriers with their ordnance, while the 36 dive-bombers attacked the two US ships. Four dive-bombers descended on Sims and the rest targeted Neosho. The destroyer was hit by three bombs, broke in half and immediately sank, taking with her all but 14 of her 192-man crew. Neosho was hit by seven bombs, and one of the dive-bombers, hit by anti-aircraft fire, crashed into the oiler. Heavily damaged and without power, Neosho was left drifting and slowly sinking but, before losing power, was able to notify Fletcher that she was under attack and in trouble, but garbled any other details as to just who or what was attacking her and gave the wrong co-ordinates for her position.

The US attack aircraft sighted Shoho a short distance to the north-east of Misima island at 10.40 and deployed to attack. The Japanese carrier was protected by four A6M and two Mitsubishi A5M single-engined fighters flying combat air patrol, as the rest of the carrier’s aircraft were being prepared below decks for an attack on the US carriers. Goto’s cruisers surrounded the carrier in a diamond formation, between 3,000 and 5,000 yards (2750 and 4575 m) off each of Shoho's 'corners'. Attacking first, Lexington's air group, led by Commander William B. Ault, hit Shoho with two 1,000-lb (454-kg) bombs and five torpedoes, causing severe damage. At 11.00, Yorktown's air group attacked the burning and now almost stationary carrier, hitting her with as many as 11 more 1,000-lb (454-kg) bombs and at least two torpedoes. Torn apart, Shoho sank at 11.35. Fearing more air attacks, Goto withdrew his warships to the north, but sent the destroyer Sazanami back at 14.00 to rescue survivors, who numbered just 203 of the carrier’s 834-man crew. Three US aircraft were lost in the attack: two SBD dive-bombers from Lexington and one from Yorktown. All of Shoho's aircraft complement of 18 was lost, but three of the combat air patrol’s pilots were able to ditch at Deboyne and survived. At 12.10, using a prearranged message to signal TF17 on the success of the mission, the Lexington SBD pilot and squadron commander Robert E. Dixon radioed 'Scratch one flat top! Signed Bob.'

The US aircraft had returned and landed on their carriers by 13.38, and within 40 minutes had been rearmed and refuelled, and were ready to take-off against the Port Moresby Invasion Force or Goto’s cruisers. Fletcher was concerned that the locations of the rest of the Japanese fleet carriers were still unknown, for he had been informed that Allied intelligence sources believed that up to four Japanese carriers might be supporting the 'Mo' (ii) operation. Fletcher concluded that by the time his scout aircraft found the remaining carriers it would be too late in the day to mount any attack on them, and therefore decided not to attempt another attack on this day and remain concealed under the thick overcast with fighters ready in defence. Fletcher turned TF17 to the south-west.

Informed of the loss of Shoho, Inoue ordered the invasion convoy to withdraw temporarily to the north and ordered Takagi, at this time located 260 miles (418 km) to the east of TF17, to destroy the US carrier forces. As the invasion convoy reversed course, it was attacked by eight USAAF B-17 bombers, but suffered no damage. Goto and Kajioka were told to assemble their ships to the south of Rossel island for a night surface battle if the US ships came within range.

At 12.40, a seaplane from Deboyne island sighted and reported Crace’s detached cruiser and destroyer force on a bearing of 175° and some 90 miles (144 km) from the island. At 13.15, an aeroplane from Rabaul sighted Crace’s force but submitted an erroneous report, stating the force contained two carriers and was located at a bearing of 205° and some 133 miles (213 km) from Deboyne island. On the basis of these reports, and still awaiting the return of all of his aircraft from attacking Neosho, Takagi turned his carriers due west at 13.30 and advised Inoue some 90 minutes later that the US carriers were at least 490 miles (790 km) to the west of his location and that he would therefore be unable to attack them that day.

Inoue’s staff ordered two groups of attack aircraft from Rabaul, already airborne since that morning, toward Crace’s reported position. The first group included 12 torpedo-armed G4M bombers and the second group comprised 19 Mitsubishi G3M 'Nell' twin-engined bombers. Both groups located and attacked Crace’s ships at 14.30 and claimed to have sunk a 'California-type' battleship and damaged another battleship and a cruiser. In reality, Crace’s ships were undamaged and shot down four of the G4M bombers. A short time later, three USAAF B-17 heavy bombers mistakenly attacked Crace’s force, but caused no damage.

At 15.26, Crace radioed Fletcher that he could not complete his mission without air support, and retired to the south to a position about 250 miles (400 km) to the south-east of Port Moresby in order to increase the range from Japanese carrier- or land-based aircraft while remaining close enough to intercept any Japanese naval forces advancing beyond the Louisiade islands group through either the Jomard Passage or the China Strait. Crace’s ships were short of fuel, and as Fletcher was maintaining radio silence (and had not informed him in advance) Crace had no idea of Fletcher’s location, status or intentions.

Shortly after 15.00, Zuikaku monitored a message from a reconnaissance aeroplane operating from Deboyne island reporting reporting, incorrectly, that Crace’s force had altered course to 120°. Takagi’s staff assumed the aircraft was shadowing Fletcher’s carriers and determined that should the Allied ships hold that course, they would be within striking range shortly before the fall of night. Takagi and Hara were determined to attack immediately with a select group of aircraft, without fighter escort, even though it meant the attacking aircraft would not return until after the arrival of darkness.

In an effort to confirm the location of the US carriers, at 15.15 Hara sent a flight of eight torpedo bombers as scouts to sweep 230 miles (370 km) to the west. At about that same time, the dive-bombers which had attacked Neosho returned and landed. Six of the weary dive-bomber pilots were told they would be immediately departing on another mission. Choosing his most experienced crews, including Takahashi, Shimazaki and Lieutenant Tamotsu Ema, at 16.15 Hara launched 12 dive-bombers and 15 torpedo-bombers with orders to fly on a heading of 277° to a distance of 320 miles (520 km). The eight scout aircraft reached the end of their 230-mile (370-km) search leg and turned back without sighting Fletcher’s ships.

At 17.47, operating under thick overcast 230 miles (370 km) to the west of Takagi’s ships, TF17 detected the Japanese attack on radar as it headed in the US ship’s direction, turned to the south-east and thus into the wind, and sent up 11 F4F fighters on a combat air patrol under the leadership of Lieutenant Commanders Paul H. Ramsey and James H. Flatley, to effect an interception. Taking the Japanese formation by surprise, the F4F fighters shot down seven torpedo-bombers and one dive-bomber, and heavily damaged another torpedo-bomber, which later crashed, at the cost of three of their own number.

Having taken heavy losses in the attack, which also scattered their formations, the Japanese attack leaders cancelled the mission after conferring by radio, and the aircraft all jettisoned their ordnance and reversed course to return to their carriers. The sun set at 18.30. Several of the Japanese dive-bombers encountered the US carriers in the darkness, at about 19.00 and, briefly confused as to their identity, circled in preparation for landing before anti-aircraft fire from TF17’s destroyers drove them away. By 20.00, TF17 and the Carrier Strike Force were about 115 miles (185 km) apart. Takagi turned on his warships' searchlights to help guide the 18 surviving aircraft back, and all had been recovered by 22.00.

In the meantime, at 15.18 and 17.18 Neosho was able to radio TF17 that she was drifting to the north-west in a sinking condition. Neosho's latter report gave the wrong co-ordinates for her position, and this hampered subsequent US rescue efforts to locate the oiler. More significantly, the news informed Fletcher his only nearby available fuel supply was gone.

As the fall of night ended aircraft operations for the day, Fletcher ordered TF17 to head to the west and prepared to launch a 360° search at first light. Crace also turned west to stay within striking range of the Louisiade islands group. Inoue directed Takagi to make sure he destroyed the US carriers on the following day, and postponed the Port Moresby landings to 12 May. Takagi elected to take his carriers 140 miles (225 km) to the north during the night so he could concentrate his morning search to the west and south, and to ensure that his carriers could provide better protection for the invasion convoy. Goto and Kajioka were unable to position and co-ordinate their ships in time to attempt a night attack on the Allied warships.

Each side expected to find the other early on the next day, and spent the night preparing tits attack aircraft for the anticipated battle as their exhausted aircrews attempted to get a few hours' sleep. Hara later told Yamamoto’s chief-of-staff, Rear Admiral Matome Ugaki, that he was so frustrated with the 'poor luck' the Japanese had experienced on 7 May that he felt like retiring from the navy.

At 06:.5 on 8 May, from a position 15 miles (185 km) to the east of Rossel island, Hara launched seven torpedo bombers to search the area bearing 140° to 230° out to a range of 290 miles (465 km) from the Japanese carriers. Assisting in the search were three H6K flying boats from Tulagi and four G4M bombers from Rabaul. At 07.00, the Carrier Strike Force turned to the south-west and was joined by two of Goto’s cruisers, Kinugasa and Furutaka, to provide additional screening support. The Port Moresby Invasion Force, Support Force, Main Body and Attack Force steered toward a rendezvous point some 45 miles (72.5 km) to the east of Woodlark island to await the outcome of the carrier battle. During the night, the warm frontal zone with low clouds which had helped to conceal the US carriers on 7 May moved to the north and east and now covered the Japanese carriers, limiting visibility to between 2.3 and 17.3 miles (3.7 and 27.8 km).

At 06.35 TF17, which was operating under Fitch’s tactical control and positioned 210 miles (330 km) to the south-east of the Louisiade islands group, launched 18 SBD aircraft to conduct a 360° search out to a range of 230 miles (370 km). The skies over the US carriers were mostly clear, with 20-mile (32-km) visibility.

At 08.20, an SBD from Lexington, piloted by Joseph G. Smith, spotted the Japanese carriers through a hole in the clouds and notified TF17. Two minutes later, one of Shokaku's search aircraft, commanded by Kenzo Kanno, sighted TF17 and notified Hara. The two forces were then about 240 mi (390 km) apart. Both sides raced to launch their attack aircraft. At 09.15, the Japanese carriers launched an attack force of 18 A6M fighters, 33 D3A dive-bombers and 18 B5N torpedo-bombers commanded by Takahashi, with Shimazaki again leading the torpedo-bombers. The US carriers launched separate attack forces: Yorktown's group comprised six F4F fighters, 24 SBD dive-bombers and nine TBD torpedo-bombers, which were on their way by 09.15; and Lexington's force of nine F4F fighters, 15 SBD dive-bombers and 12 TBD torpedo-bombers was off at 09.25. Both the Japanese and US carrier warship forces turned to head directly for each other’s location at high speed in order to shorten the distance their aircraft would have to cover on their return flights.

Yorktown's dive-bombers, led by William O. Burch, reached the Japanese carriers at 10.32, and paused to allow the slower torpedo squadron to arrive so that they could conduct a simultaneous attack. At this time, [e[Shokaku and Zuikaku were about 10,000 yards (9150 m) apart, with Zuikaku hidden under a rain squall of low-hanging clouds. The two carriers were protected by combat air patrol of 15 A6M fighters. Yorktown's dive-bombers began their attacks at 10.57 on Shokaku and hit the manoeuvring carrier with two 1,000-lb (454-kg) bombs, tearing open the forecastle and causing heavy damage to the carrier’s flight and hangar decks. Yorktown's torpedo-bombers missed with all of their ordnance. Two US dive-bombers and two A6M fighters were shot down during the attack.

Lexington's aircraft arrived and attacked at 11.30. Two dive-bombers attacked Shokaku, hitting the carrier with one 1,000-lb (454-kg) bomb and causing more damage. Two other dive-bombers dived on Zuikaku, but their bombs missed the Japanese carrier. The rest of Lexington's dive-bombers were unable to find the Japanese carriers in the heavy clouds. Lexington's TBD torpedo-bombers missed Shokaku with all 11 of their torpedoes. The 13 A6M fighters on patrol at this time shot down three F4F fighters.

With her flightdeck heavily damaged and 223 of her crew killed or wounded, and having also suffered explosions in her aviation fuel storage tanks and an engine repair workshop destroyed, Shokaku was unable to conduct further aircraft operations. Her captain, Takatsugu Jojima, requested permission from Takagi and Hara to withdraw from the battle, and the former authorised him to do so. At 12.10, Shokaku, accompanied by two destroyers, retired to the north-east.

At 10.55, Lexington's CXAM-1 radar detected the inbound Japanese aircraft at a range of 78 miles (126 km) and vectored nine F4F fighters to intercept. Expecting the Japanese torpedo-bombers to be at a much lower altitude than they actually were, six of the Wildcats were stationed too low, and thus missed the Japanese aircraft as they passed overhead. Because of the heavy losses in aircraft suffered during the previous night, the Japanese could not execute a full torpedo attack on both carriers. Lieutenant Commander Shigekazu Shimazaki, commanding the Japanese torpedo-bombers, sent 14 to attack Lexington and four to attack Yorktown. An F4F shot down one and patrolling SBD aircraft (eight from Yorktown and 15 from Lexington) destroyed three more of the Japanese torpedo-bombers as they descended to attack position. In return, escorting A6M fighters shot down four of Yorktown's SBD aircraft. One of the survivors, Swede Vejtasa, claimed three A6M fighters during the onslaught, but none of the Japanese fighters was lost.

The Japanese attack began at 11.13 as the carriers, steaming 3,000 yards (2745 m) apart, and their escorts opened fire with their anti-aircraft guns. The four torpedo-bombers which attacked Yorktown all missed. The remaining torpedo-bombers undertook a pincer attack on Lexington, which had a much larger turning radius than Yorktown, and at 11.20 hit her with two Type 91 torpedoes. The first torpedo buckled the port aviation fuel tanks and, undetected, fuel vapour spread into surrounding compartments. The second torpedo ruptured the port water main, reducing water pressure to the three forward firerooms and forcing the associated boilers to be shut down. The ship could still make 24 kt with her remaining boilers. Four of the Japanese torpedo-bombers were shot down by anti-aircraft fire.

The 33 Japanese dive-bombers circled to attack from upwind, and thus did not begin their dives from 14,100 ft (4300 m) until three to four minutes after the torpedo-bombers had begun their attacks. Shokaku's 19 dive-bombers, under Takahashi, targeted Lexington while the remaining 14, directed by Tamotsu Ema, targeted Yorktown. Escorting A6M fighters shielded Takahashi’s aircraft from four of Lexington's combat air patrol F4F fighters which attempted to intervene, but two F4F fighters circling above Yorktown were able to disrupt Ema’s formation. Takahashi’s bombers further damaged Lexington with two bomb hits and several near misses, causing fires which had been contained by 12.33. At 11.27, Yorktown was hit in the centre of her flightdeck by a single 551-lb (250-kg) semi-armour-piercing bomb, which penetrated four decks before detonating and causing severe structural damage to an aviation fuel compartment and killing or seriously wounding 66 men, as well as damaging the superheater boilers which rendered them inoperable. Up to 12 near misses damaged Yorktown's hull below the waterline. Two of the dive-bombers were shot down by an F4F during the attack.

As the Japanese aircraft completed their attacks and began to withdraw, believing that they inflicted fatal damage on both of the US carriers, they ran a gauntlet of F4F and SBD aircraft, and in the ensuing aerial duels the USA lost three SBD and three F4F aircraft, while the Japanese lost three B5N, one D3A and one A6M machines. By 12.00, the US and Japanese attack groups were on their way back to their respective carriers. During their return, aircraft from the two adversaries passed each other in the air, resulting in more air-to-air combat: Kanno’s and Takahashi’s aircraft were shot down, killing both of them.

The attack forces, which included many damaged aircraft, reached and landed on their respective carriers between 12.50 and 14.30. Despite their damage, Yorktown and Lexington were both able to recover aircraft from their returning air groups. During recovery operations, for various reasons the USA lost an additional five SBD, two TBD and one F4F aircraft, and the Japanese two A6M, five D3A and one B5N aircraft. Some 46 of the original 69 Japanese aircraft returned from the mission and landed on Zuikaku, and of these, three A6M, four D3A and five B5N aircraft were deemed damaged beyond repair and were immediately jettisoned.

As TF17 recovered its aircraft, Fletcher assessed the situation. The returning aircrews reported that they had severely damaged one carrier, but that another had escaped damage. Fletcher noted that both his carriers had suffered damage and that his air groups had sustained high losses among their fighters. Fuel was also a concern as a result of Neosho's loss. At 14.22, Fitch notified Fletcher that he had reports of two undamaged Japanese carriers and that this was supported by radio intercepts. Believing that he faced overwhelming Japanese carrier superiority, Fletcher decided to withdraw TF17 from the battle. Fletcher radioed MacArthur the approximate position of the Japanese carriers and suggested that land-based bombers be used to attack them.

At about 14.30, Hara informed Takagi that only 24 A6M, eight D3A and four B5N aircraft from the carriers were currently operational. Takagi was also concerned about his ships' fuel levels: his cruisers were at 50% and some of his destroyers were as low as 20%. At 15.00, Takagi notified Inoue his aircraft had sunk two US carriers (Yorktown and a 'Saratoga' class ship) but heavy losses in aircraft meant he could not continue to provide air cover for the invasion. Inoue, whose reconnaissance aircraft had sighted Crace’s ships earlier that day, recalled the invasion convoy to Rabaul, postponed 'Mo' (ii) to 3 July, and ordered his forces to assemble at a position to the north-east of the Solomon islands group to begin the 'Ry' operation. Zuikaku and her escorts turned toward Rabaul while Shokaku headed for Japan.

On board Lexington, damage-control parties put out the fires and restored the carrier to operational condition, but at 12.47, sparks from unattended electric motors ignited aviation fuel fumes near the ship’s central control station. The resulting explosion killed 25 men and started a large fire. Around 14.42, there was another large explosion, and this started a second severe fire. A third explosion occurred at 15.25, and at 15.38 the ship’s crew reported that the fires were uncontrollable. Lexington's crew began to abandon ship at 17.07. After the carrier’s survivors, including Fitch and the ship’s captain, Frederick C. Sherman, had been recovered, at 19.15 the destroyer Phelps fired five torpedoes into the burning ship, which sank in 14,400 ft (4390 m) of water. Some 216 of the carrier’s 2,951-man crew went down with the ship, along with 36 aircraft. Phelps and the other assisting warships left immediately to rejoin Yorktown and her escorts, which departed at 16.01, and TF17 retired to the south-west. Later that evening, MacArthur informed Fletcher that eight of his B-17 bombers had attacked the invasion convoy, which was now retiring to the north-west.

That evening, Crace detached Hobart, which was critically short of fuel, and the destroyer Walke, which was suffering engine problems, to proceed to Townsville. Crace overheard radio reports saying the Japanese invasion convoy had turned back but, unaware that Fletcher had withdrawn, remained on patrol in the Coral Sea with the rest of TG17.3 in case the Japanese invasion force resumed its advance toward Port Moresby.

On 9 May, TF17 altered course to the east and proceeded out of the Coral Sea via a route to the south of New Caledonia. Nimitz ordered Fletcher to return Yorktown to Pearl Harbor as soon as possible after refuelling at Tongatabu. During the day, USAAF bombers attacked Deboyne island and Kamikawa Maru, inflicting unknown damage. In the meantime, having heard nothing from Fletcher, Crace deduced that TF17 had departed the area. At 01.00 on 10 May, hearing no further reports of Japanese ships advancing toward Port Moresby, Crace turned toward Australia and arrived at Cid Harbour, 150 miles (240 km) to the south of Townsville, on 11 May.

At 22.00 on 8 May, Yamamoto had ordered Inoue to turn his forces around, destroy the remaining Allied warships, and complete the invasion of Port Moresby. Inoue did not cancel the recall of the invasion convoy, however, but did order Takagi and Goto to pursue the remaining Allied warship forces in the Coral Sea. Critically short of fuel, Takagi’s warships spent most of 9 May refuelling from the fleet oiler Toho Maru. Late in the evening of 9 May, Takagi and Goto headed to the south-east, then to the south-west into the Coral Sea. Flying boats from Deboyne island assisted Takagi in searching for TF17 on the morning of 10 May, when Fletcher’s and Crace’s ships were already well on their way out of the area. At 13.00 on 10 May, Takagi concluded that the Allied forces were gone and decided to turn back toward Rabaul. Yamamoto now concurred with Takagi’s decision and ordered Zuikaku to return to Japan for the replenishment of her air group. At the same time, Kamikawa Maru packed up and departed Deboyne island. At 12.00 on 11 May, a US Navy Consolidated PBY twin-engined flying boat on patrol from Nouméa sighted the drifting Neosho, and the US destroyer Henley responded to rescue 109 survivors from Neosho and 14 from Sims later in that day, then sank the tanker with gunfire.

On 10 May, 'Ry' began. After the operation’s flagship, the minelayer Okinoshima, had been sunk by the US submarine S-42 on 12 May, the landings were postponed until 17 May. In the meantime, Halsey’s TF16 reached the South Pacific near Efate and, on 13 May, headed to the north to contest the Japanese approach to Nauru and Ocean islands. On 14 May, After obtaining intelligence about the Combined Fleet's upcoming operation against Midway, Nimitz ordered Halsey to make sure that Japanese scout aircraft sighted his ships on the following day, after which he was immediately to return to Pearl Harbor. At 10.15 on 15 May, a Kawanishi reconnaissance flying boat from Tulagi sighted TF16 some 512 miles (824 km) to the east of the Solomon islands group. Halsey’s feint worked: fearing a carrier air attack on his exposed invasion forces, Inoue immediately cancelled 'Ry' and ordered his ships back to Rabaul and Truk. On 19 May TF16, which returned to the Efate area to refuel, turned toward Pearl Harbor and arrived there on 26 May. Yorktown reached Pearl Harbor on the following day.

Shokaku reached Kure in the Japanese home islands on 17 May, almost capsizing en route during a storm as a result of her battle damage. Zuikaku arrived at Kure on 21 May, having made a brief stop at Truk on 15 May. Acting on signals intelligence, the USA had placed eight submarines along the projected route of the carriers' return paths to Japan, but the boats were unable to make any attacks. Japan’s naval general staff estimated that it would take two to three months to repair Shokaku and replenish the two carriers' air groups, so both carriers would be unable to participate in Yamamoto’s forthcoming Midway operation. The two carriers rejoined the Combined Fleet on 14 July and were key participants in subsequent carrier battles against US forces. The five 'I' class submarines supporting the 'Mo' (ii) operation were retasked to support an attack on Sydney harbour three weeks later as part of a campaign to disrupt Allied supply lines. On its passage to Truk, the submarine I-28 was torpedoed on 17 May by the US submarine Tautog and sank with all hands.

Both sides publicly claimed victory after the 'Battle of the Coral Sea'. In terms of ships lost, the Japanese had won a tactical victory by sinking the US fleet carrier Lexington, one oiler and one destroyer totalling 41,826 tons for their own loss of one light carrier, one destroyer, and several smaller warships totalling 19,000 tons. At that time. Lexington represented one-quarter of the US carrier strength in the Pacific. The Japanese public was informed of the victory with an overstatement of the US losses and an understatement of their own.

At the strategic level, however, the battle was an Allied victory as it averted the seaborne invasion of Port Moresby, lessening the threat to the supply lines between the USA and Australia. Although the withdrawal of Yorktown from the Coral Sea conceded the field, the Japanese were forced to abandon the operation that had initiated the 'Battle of the Coral Sea' in the first place.

The battle marked the first time that a Japanese invasion force had been turned back without achieving its objective, which greatly lifted the morale of the Allies after a series of defeats by the Japanese during the initial six months of the Pacific War. Port Moresby was vital to Allied strategy and its garrison could well have been overwhelmed by the experienced Japanese invasion troops. The US Navy also exaggerated the damage it inflicted, which later caused the press to treat its reports of the 'Battle of Midway' with more caution.

The results of the battle had a substantial effect on the strategic planning of both sides. Without a hold in New Guinea, the subsequent Allied advance, arduous as it was, would have been even more difficult. For the Japanese, who focused on the tactical results, the battle was seen as merely a temporary setback. The results of the battle confirmed the low opinion held by the Japanese of US fighting capability and supported their overconfident belief that future carrier operations against the USA were assured of success.[98]

One of the most significant effects of the 'Battle of the Coral Sea' was the loss of Shokaku and Zuikaku to Yamamoto for his planned battle in the air with the US carriers at Midway. (Shoho was to have been employed at Midway in a tactical role supporting the Japanese invasion ground forces.) Although Zuikaku was undamaged, she had lost a large number of aircraft in the battle, and the Japanese apparently did not even consider trying to include Zuikaku in the forthcoming operation. No effort appears to have been made to combine e]Shokaku's surviving aircrews with Zuikaku's air groups, as this was contrary to Japanese doctrine, or quickly to provide Zuikaku with replacement aircraft. Shokaku herself was unable to conduct further aircraft operations, with her flightdeck heavily damaged, and required almost three months of repair in Japan.

The Japanese believed that they had sunk two carriers in the 'Battle of the Coral Sea', but this still left the US Navy with at least two more carriers, Enterprise and Hornet, with which to help defend Midway. In fact, Yorktown had only been damaged, but she had also lost a large number of aircraft and aircrew in the battle. Unlike the Japanese, the US Navy made a maximum effort to make Yorktown available for the coming battle. Although the damage had been estimated a requiring 90 days to repair, Nimitz gave the shipyard only three days, and only the most critical repairs were made to make the ship seaworthy. Yorktown departed Pearl Harbor with three of her boilers inoperative and a maximum speed of 27 kt. Unlike the Japanese, the US Navy was willing to put one aircraft carrier’s air group on another ship. To make up aircraft losses in the 'Battle of the Coral Sea', three of Yorktown's four squadrons were sent ashore and replaced by squadrons from Saratoga, which had been sent to the USA’s west coast for repairs after being torpedoed by a Japanese submarine. Yorktown would therefore re-enter battle with its own scouting squadron but Saratoga's torpedo-bomber, dive-bomber and fighter squadrons.

The US aircraft carriers had slightly larger aircraft complements than the Japanese carriers which, when combined with the land-based aircraft at Midway, the availability of Yorktown and the unavailability of two Japanese carriers, meant that the Imperial Japanese navy and the US Navy would have a near-parity in aircraft for the impending battle. At Midway, aircraft flying from Yorktown played crucial roles in the US victory, in which Yorktown's aircraft sank [e[Soryu, located Hiryu and helped Enterprise's aircraft to sink Hiryu. Yorktown also absorbed both Japanese air counterattacks at Midway which otherwise would have been directed at Enterprise and Hornet.

Several historians believe that Yamamoto made a significant strategic error in his decision to support 'Mo' (ii) with strategic assets. Since Yamamoto had decided the decisive battle with the USA was to take place at Midway, he should not have diverted any of his important assets, especially fleet carriers, to a secondary operation such as 'Mo' (ii). Yamamoto’s decision meant that Japanese naval forces were weakened just enough in both the 'Battle of the Coral Sea' and 'Battle of Midway' to allow the Allies to defeat them in detail. If either operation was important enough for the commitment of fleet carriers, then all of the Japanese carriers should have been used in each in order to ensure success. By committing crucial assets to 'Mo' (ii), Yamamoto made the more important Midway operation dependent on the secondary operation’s success.

Moreover, Yamamoto apparently missed the other implications of the 'Battle of the Coral Sea': the unexpected appearance of US carriers in exactly the right place and time (as a result of cryptanalysis) to contest the Japanese effectively, and US Navy carrier aircrews demonstrating sufficient skill and determination to inflict significant damage on the Japanese carrier forces. These would be repeated at Midway, for the same reason, and as a result Japan lost four fleet carriers, the core of its naval offensive forces, and thereby lost the strategic initiative in the Pacific War. As a result of US industrial strength, once Japan lost its numerical superiority in carrier forces as a result of Midway, Japan could never regain it.

The Australians and US forces in Australia were initially disappointed with the outcome of the 'Battle of the Coral Sea', fearing that the 'Mo' (ii) operation was merely the precursor to an invasion of the Australian mainland, and the setback to Japan was only temporary. In a meeting late in May, the Australian Advisory War Council described the battle’s result as 'rather disappointing' in light of the fact that the Allies had advance notice of the Japanese intentions. MacArthur provided the Australian prime minister, John Curtin, with his assessment of the battle, stating that 'all the elements that have produced disaster in the Western Pacific since the beginning of the war' were still present as Japanese forces could strike anywhere if supported by major elements of the Imperial Japanese navy.

As a result of their severe carrier losses in the 'Battle of Midway', the Japanese were unable to support another attempt to invade Port Moresby from the sea, forcing Japan to attempt an overland seizure of Port Moresby. Japan began its land offensive toward Port Moresby along the Kokoda Track on 21 July from Buna and Gona. By then, the Allies had reinforced New Guinea with additional troops (primarily Australian) starting with the Australian 14th Brigade which embarked at Townsville on 15 May. The added forces slowed and eventually halted the Japanese advance toward Port Moresby in September 1942, and defeated the 'Re' attempt by the Japanese to overpower an Allied base at Milne Bay.

In the meantime, the Allies learned in July that the Japanese had begun building an airfield on Guadalcanal. Operating from this base the Japanese would be able to threaten the shipping supply routes to Australia from the USA. To prevent the Japanese plan from reaching fruition, the USA chose Tulagi and nearby Guadalcanal as the target of their 'Watchtower' first offensive. The failure of the Japanese to take Port Moresby, and their defeat at Midway, had the effect of dangling their base at Tulagi and Guadalcanal without effective protection from other Japanese bases. Tulagi and Guadalcanal were four hours flying time from Rabaul, the nearest large Japanese base. Three months later, on 7 August, 11,000 US Marines landed on Guadalcanal, and 3,000 US Marines landed on Tulagi and nearby islands. The Japanese troops on Tulagi and nearby islands were outnumbered and killed almost to the last man in the 'Battle of Tulagi and Gavutu-Tanambogo', and the US Marines on Guadalcanal captured the airfield under construction by the Japanese. Thus began the Guadalcanal and Solomon islands campaigns that resulted in a series of attritional combined-arms battles between Allied and Japanese forces over the next year which, in tandem with the New Guinea campaign, eventually neutralised the Japanese defences in the South Pacific, inflicted irreparable losses on the Japanese military, and especially their navy, and contributed significantly to the Allies' eventual victory over Japan.

The delay in the advance of Japanese forces also allowed the US Marine Corps to land on Funafuti in the Ellice islands group on 2 October 1942, after which 'Seabee' naval construction troops built airfields on three of the island group’s atolls from which USAAF Consolidated B-24 Liberator four-engined heavy bombers of the US 7th Army Air Force operated. The atolls of the Ellice islands served as a staging post during the preparation for the 'Battle of Tarawa' and the 'Battle of Makin' that began on 20 November 1943 as the start of the 'Galvanic' operation.

As noted above, the 'Battle of the Coral Sea' was history’s first naval engagement in which the participating ships never sighted or fired directly at each other. Instead, manned aircraft acted as the offensive artillery for the ships involved. Thus, the respective commanders were participating in a new type of warfare, carrier-versus-carrier, with which neither had any experience. The commanders 'had to contend with uncertain and poor communications in situations in which the area of battle had grown far beyond that prescribed by past experience but in which speeds had increased to an even greater extent, thereby compressing decision-making time.' Because of the greater speed with which decisions were required, the Japanese were at a disadvantage as Inoue was too far away at Rabaul to effectively direct his naval forces in real time, in contrast to Fletcher who was on the scene with his carriers. Moreover, the Japanese admirals involved were often slow to communicate important information to one another.

The experienced Japanese carrier aircrews performed better than those of the USA, and achieved greater results with an equivalent number of aircraft. The Japanese attack on the US carriers on 8 May was better co-ordinated than the US attack on the Japanese carriers. However, the Japanese suffered considerably higher losses among their carrier aircrews, losing 90 men killed in the battle compared with 35 on the US side. Japan’s cadre of highly skilled carrier aircrews with which it began the war were, in effect, irreplaceable because of the small size and slow pace of of its training programmes, and the absence of a pool of experienced reserves or advanced training programmes for new airmen. The 'Battle of the Coral Sea' started a trend which resulted in the irreparable attrition of Japan’s veteran carrier aircrews by the end of October 1942.

The USA did not perform as expected, but it learned from its mistakes in the battle and quickly initiated improvements to its carrier tactics and equipment, including fighter tactics, attack co-ordination, torpedo-bomber aircraft and defensive tactics such as anti-aircraft artillery, which contributed to better results in later battles. Radar gave the US Navy a limited advantage in this battle, but its value to the US Navy increased over time as the technology improved and the Allies learned how to employ it more effectively. Following the loss of Lexington, improved methods for containing aviation fuel and better damage-control procedures were implemented by the US Navy. Co-ordination between the Allied land-based air forces and the US Navy was poor during this battle, but this too improves steadily.

Japanese and US carriers faced off against each other again in the 'Battle of Midway', the 'Battle of the Eastern Solomons' and the 'Battle of the Santa Cruz Islands' in 1942; and the 'Battle of the Philippine Sea in 1944. Each of these battles was strategically significant, to varying degrees, in deciding the course and ultimate outcome of the Pacific War.