Eighty years ago, Charlie Rowland was serving as intelligence aide to the U.S. military attaché to Australia when the Battle of the Coral Sea was fought in waters off the southern continent. The 4–8 May 1942 naval clash became the first in which the contending warships never saw one another. Ruminating with a Coral Sea veteran in the wake of the battle’s 50th anniversary, Rowland commented that God had had a big hand in turning the outcome in the Allies’ favor.1
In fact, the extraordinary battle featured no shortage of oddities. They include Japanese scout planes misidentifying a U.S. fleet oiler as an aircraft carrier, after which she was duly attacked by carrier planes. Crippled by seven bomb hits, eight near misses, and a crashed aircraft, the oiler stayed afloat for four days; a destroyer rescued survivors. Another oddity was how an error in a coded message resulted in U.S. carrier planes attacking a Japanese light carrier instead of the enemy’s fleet vessels. Then there were the Nipponese planes that, in gathering darkness, lined up in a landing pattern behind a U.S. carrier, the Yorktown (CV-5). But it still may be worth asking the question: Did God, Lady Luck, or sound intelligence play the biggest part in the battle?
‘Tex’ Biard’s Problems
Behind the veneer of the Battle of the Coral Sea, as with the Battle of Midway fought a month later, there is a quite crucial intelligence story. The tale begins in February 1942, about the time Commander-in-Chief, Pacific (CINCPAC) Admiral Chester W. Nimitz began sending single-carrier task forces to raid Japanese positions in the Central Pacific and New Guinea area. Naval intelligence at Pearl Harbor—represented by CINCPAC’s fleet intelligence officer; the 14th Naval District intelligence office; and, for communications intelligence, Station Hypo (also known as the CINCPAC Combat Intelligence Unit)—decided to place radio intelligence (RI) detachments on board the flagships of each participating carrier task force. With two experienced radiomen to listen for Japanese transmissions and an officer to liaise with the commanding admiral, manage the RI unit, and supply translations or decoding, the detachments served as the U.S. fleet’s ears on the enemy. In mid-February, Lieutenant Forrest R. “Tex” Biard, a senior linguist from Hypo, went to the flagship of Task Force 17, the Yorktown, which was dispatched to the Coral Sea.
Tex Biard had two problems. First, when the Yorktown sailed, Station Hypo and the other U.S. codebreakers had yet to complete their reconstruction of the Japanese naval code, which they called JN-25(b). Until he had detailed knowledge of the Japanese code, Biard could not perform actual decryptions on board the carrier, which limited the radio detachment’s utility. For the time being, the intelligence unit’s radiomen were restricted to listening to unencoded Japanese transmissions, and Biard to broadcasts from Radio Tokyo. In addition, the lack of current information on JN-25 left Biard with little to say when asked for information.
That put the lieutenant on a very poor footing with Task Force 17’s commander, Rear Admiral Frank Jack Fletcher—Biard’s second problem. The admiral’s chief of staff had found the RI unit a working space on the same deck of the Yorktown’s island that housed the flag bridge and Fletcher’s sea cabin. The narrow island required the admiral to cross the radio space each time he walked from cabin to command center.
Biard, the most junior officer on Fletcher’s staff, could disclose little about his assignment. He became the man who did invisible work and aroused the admiral’s ire. The day duly came when Fletcher, at a luncheon with his staff, asked his radio intelligence chief to explain codebreaking in front of the whole crowd. In keeping with security protocols, Biard pretended there was no story. He later approached the admiral in private only to be subjected to a dressing down.
On 6 March, the USS Lexington (CV-2) with its Task Force 11 rendezvoused with Task Force 17 for operations that were to include a strike on shipping at Rabaul on New Britain, the main base of the Imperial Japanese Navy (IJN) in the South Pacific. But the next day, the enemy landed troops on New Guinea’s northern coast, resulting in a change of plans. On 10 March, aircraft from the Yorktown and Lexington attacked ships of the invasion fleet off Lae and Salamaua.
The carriers then parted ways, the Lexington to Pearl Harbor and the Yorktown to Tonga’s main island, Tongatabu (which the Americans knew by the geographical codename Bleacher), to receive upkeep and essential repairs to their fighter planes. Fletcher’s ships arrived in the Tonga Islands on 20 April and stayed for a week. Today we think of Tonga—the Friendly Islands—as the victim of a disastrous January 2022 volcanic eruption and tsunami. Tex Biard remembered the luau there hosted by the brother of Tonga’s queen, where the roast pork came completely unsalted. He considered it inedible.
Divining Japan’s Plan
While the Yorktown had been steaming in the South Pacific, the wizards of Station Hypo and their colleagues wrestled with the Japanese codes. On 23 March, Station Belconnen, the radio intelligence unit at Melbourne, Australia (formerly Station Cast, located in the Philippines), contributed a list of Japanese place-name designators, which identified the letter “R” with locations in the Australia region. Two days later, Hypo and Belconnen intercepted references to “RZP.” The cryptologists’ increasing understanding of the JN-25 code made the underlying text intelligible. Commander Joseph J. Rochefort, who led Hypo, argued the designator stood for Port Moresby, a key Allied port and airbase complex on the south coast of New Guinea. This was the first indication of Japanese interest in Australia or New Guinea.
More pieces fell into place. Japanese messages on 3 April spoke of air reinforcements and unit reorganization at Rabaul. A 7 April dispatch about repairs to the aircraft carrier Kaga revealed the Japanese planned an RZP “campaign.” This operation was soon linked with the codename MO. Because the Kaga was known to have participated in the Pearl Harbor attack, her being connected to the RZP campaign banished doubts that something significant was afoot. The Kaga did not, in fact, participate in Operation MO, but her role authenticating the idea of an operation proved crucial. As the Yorktown and Fletcher’s Task Force 17 had reached and anchored at Tonga, codebreakers discovered references to an “MO Occupation Force” and learned of a different, new Japanese carrier and a full division of heavy cruisers associated with it.
Commander Rochefort steadfastly argued that the enemy MO campaign would aim to capture Port Moresby. As the picture filled in, it appeared that two other Pearl Harbor attackers, the carriers Sho‒kaku and Zuikaku, also would participate and that the Japanese intended to create a seaplane base on Tulagi, an island in the southern Solomons across from Guadalcanal. The codebreakers missed the intercept in which the anticipated mission of the Kaga was canceled, but aside from that, U.S. intelligence developed a pretty complete picture of Japanese intentions. After the Yorktown left the Friendly Islands, Lieutenant Biard recalled that “the return trip . . . to our Coral Sea patrol area was marked by an increasing flurry of dispatches from Pearl saying the Japanese were believed to be preparing to move on and occupy Port Moresby.”2
Other Intel Efforts
Messages on the codebreakers’ closely held circuit demonstrate the care with which Allied commanders observed the goings-on of the Japanese. One CINCPAC message on 20 March had reported the results of aerial observation over Rabaul Harbor. A heavy and a light cruiser with a destroyer and a half-dozen patrol bombers were in the port, and seven twin-engine bombers were at one of the nearby airfields. Intelligence analysts monitored the Japanese operation to seize Lae and Salamaua. In early April, another cable reported enemy moves to take over points in the Northern Solomons and the presence at Rabaul of Rear Admiral Sadayoshi Yamada, chief of the 25th Air Flotilla, headquartered at the base. On 14 April, British intelligence warned that part or all of the First Air Fleet, the IJN’s carrier force that had been raiding in the Indian Ocean, appeared to be connected with an operation against RZP.
These reports were just a reflection of U.S. naval thinking. In Washington, the intelligence section of the Office of the Chief of Naval Operations (OP-16, more formally known as the Office of Naval Intelligence) produced a daily summary titled Japanese Naval Activities. On 18 April, in evaluating the possibility the Japanese might raid the U.S. West Coast or reattack Hawaii (in revenge for that day’s Doolittle Raid against Japan), the summary concluded that “such an undertaking would probably postpone for some time the expected advance into the Australian sphere, for which the Japanese continue to make preparations.”3
Admiral Ernest J. King, Chief of Naval Operations and Commander-in-Chief, U.S. Fleet (COMINCH), intervened that day, personally clearing a dispatch warning other commands that radio intelligence had discovered an error in decrypting an earlier message and clarifying that the date for the Japanese offensive would be 3 or 4 May, not 21 April, as had been reported. Station Hypo’s radio digest for 21 April noted the very units predicted to participate in Operation MO were assembling at the Japanese Central Pacific base at Truk Atoll. Repeating the “impending concentration” report, CINCPAC went on to announce an “IMPENDING OPERATION CENTERING [in the] NEW BRITAIN AREA WILL START VERY SOON.”4 The 26 April Japanese Naval Activities summary noted enemy air raids on Port Moresby, Tulagi, and northern Australia’s Port Darwin and projected them as opening phases of the expected offensive.
Estimating the Situation
The lead-up to the Coral Sea battle featured some of the deepest tactical and strategic calculations of the Pacific war. Admiral King, who wanted to avoid conducting the conflict at long distance, inaugurated a practice of periodic conferences with his Pacific Fleet commander, Nimitz. The first of these was set to take place in San Francisco on 25 April. Nimitz convened his CINCPAC staff about a week earlier to review the intel. The CINCPAC command summary for that day forecast the Japanese offensive commencing around the end of the month. Nimitz accepted Rochefort’s hypothesized enemy plan, including both the Port Moresby offensive and a subsequent Central Pacific thrust, which would trigger the Battle of Midway.
To help Nimitz clarify his thinking, his staff began work on a formal estimate of the situation, which was completed in time for the San Francisco conference. There had been some differences between CINCPAC and COMINCH estimates on the timing of Operation MO. They now agreed that 3 May would mark the starting date. The Pacific Fleet commander, not sure he could concentrate enough force to stop the Japanese, dispatched Task Force 11, built around the Lexington and now commanded by Rear Admiral Aubrey N. Fitch. It left Pearl Harbor on 16 April. Fitch was to join Fletcher’s Task Force 17 at a mid-ocean rendezvous, “Point Buttercup,” at the edge of the Coral Sea and about 1,700 nautical miles from Tongatabu.
Buttercup’s location, provisions for fueling groups for the carriers at sea, specifics about a supporting base network, an analysis of friendly versus enemy strengths and weaknesses, plus a detailed rundown of expected IJN strength—including extra forces that could potentially intervene—all appeared in the estimate. The substance of the intelligence on the Japanese came from Station Hypo through Captain Edwin T. Layton, CINCPAC’s fleet intelligence officer.
A further staff huddle at Pearl Harbor on 22 April examined the details. Layton recalled this as “one of the most critical CINCPAC staff meetings of the war.” After drawing attention to Japanese strength advantages, he added, “We could count on radio intelligence to reveal [their] direction and deployment,” and concluded, “this was the crucial factor that persuaded Nimitz to commit his outnumbered forces.”5
On 29 April, Station Hypo decrypted an operations order from Admiral Isoroku Yamamoto, the Japanese Combined Fleet Commander-in-Chief. In the nature of an eve-of-battle exhortation, it also settled any doubts Port Moresby was the enemy’s target. After that, the pace of developments quickly picked up.
Task Forces 11 and 17 rendezvoused on 1 May. Thereafter, when Fitch took what Fletcher thought was too much time to refuel, they separated, operating within supporting distance of each other, with fleet oilers close by.
On 2 May, a Yorktown scout plane spotted a Japanese submarine on the surface to the west. This brought on another confrontation between Admiral Fletcher and radio spy Biard. Fletcher demanded to know if the submarine had sent a sighting report. Biard had heard nothing and said so. But Admiral Fitch’s radio intelligence unit claimed it had overheard a report. That unit was led by Lieutenant Commander Ranson Fullinwider, who had served with Fletcher a decade earlier in the Asiatic Fleet. Fletcher chose to believe Fullinwider. Neither Station Hypo nor Belconnen intercepted any such submarine report, and a postwar inquiry by U.S. authorities also failed to disclose such a notice.6
The next morning, the Japanese landed at Tulagi, which Fletcher answered on 4 May with a sudden carrier raid on the invasion force, crippling an enemy destroyer and sinking a couple of minesweepers. The Yorktown and Lexington rejoined on 5 May but separated again when Fletcher refueled. Had the Japanese commander, Vice Admiral Takagi Takeo, then conducted long-range air searches, Fletcher’s task force would have been spotted. Meanwhile, a scout plane from Rabaul spotted the Yorktown and sent a sighting report, which the Japanese carriers never received. For a time, the adversaries closed to within 70 miles of each other without either side being aware of the other’s presence.
Climax of the Contest
A key development on 6 May was the interception of a dispatch from the MO Invasion Force revealing its expected position at a certain time the next day. Fletcher’s morning search on 7 May covered that area and found some heavy cruisers of the Japanese Covering Group. The scout plane’s pilot mistakenly encoded his report so it listed two aircraft carriers. Admiral Fletcher supposed the enemy’s Carrier Striking Force had been located and immediately dispatched a maximum strike force from the Yorktown and Lexington. On a mistaken mission, the carrier planes found and blasted the light carrier Sho‒ho‒. Aviators joyfully reported, “Scratch one flattop!”7
The Japanese matched suit with their own mistaken main strike that day after receiving an erroneous report from a scout plane. Passing the U.S. task force, the aircraft hit the oiler Neosho (AO-23) and destroyer Sims (DD-409). Both were left crippled, but neither was a priority target. The enemy managed a late-afternoon second wave carrier-plane sortie that found no Allied ships but in the gathering dusk blundered into the U.S. carriers’ combat air patrols. Fletcher’s fighters downed some of the Japanese planes, and others became so disoriented in the gloom they attempted to land on the American carriers, with further losses from U.S. antiaircraft guns.
The morning of 8 May brought the battle’s climax. Both sides now sought enemy carrier targets, both had lost aircraft, both had gotten previous sighting reports, both force commanders were under pressure for results. Scout planes from the Lexington took to the air at 0625. The first scout found the Japanese about two hours later. Before his report was complete and reached Admiral Fletcher, Tex Biard’s radiomen intercepted the report of a Japanese sighting of the U.S. carriers. Fletcher ordered an air strike within one minute of receiving the U.S. scout’s 0838 message. In all, 82 U.S. planes attacked the Japanese before noon. Hit by three 1,000-pound bombs, the Sho‒kaku was heavily damaged. The Zuikaku escaped unscathed, but her air group would suffer heavy losses. In the meantime, 90 Japanese planes attacked Task Force 17, damaging the Yorktown and wounding the Lexington so grievously that hours later her fires set off internal explosions.
The battle ended with Americans losing a fleet carrier, an oiler, and a destroyer against Japanese losses of a light carrier, a minelayer, a couple of sweepers, an oiler, and a destroyer. Both sides lost aircraft and had other ships damaged. But the Americans had turned back the Japanese attempt to capture Port Moresby, and U.S. commanders had acquired priceless experience in the cadence and logic of carrier air operations in combat that played a crucial role at the Battle of Midway.
On the Japanese side, all three of the aircraft carriers at Coral Sea missed Midway. The Sho‒ho‒ lay on the bottom of the sea; the Sho‒kaku and Zuikaku returned to Japan, the former to undergo major repairs and the latter to have her air group reconstituted. Their presence at Midway might have turned the tide. Conversely, the Americans were able to repair the Yorktown and get her into their Midway lineup. Now, as to whether all this was mostly due to God’s grace, Lady Luck, or the spymasters is for you to judge.
1. Charlie Rowland letter to William F. Surgi, 9 September 1995, copy courtesy of Jane Smith-Hutton.
2. Naval Cryptologic Veterans Association, “The Pacific War through the Eyes of Forrest R. ‘Tex’ Biard,” Cryptolog 10, no. 2 (Winter 1989): 9.
3. Department of the Navy, Office of the Chief of Naval Operations, “Japanese Naval Activities, Summary as of 0800, April 18, 1942 (hereafter cited as “Japanese Naval Activities”), 1, Franklin D. Roosevelt Presidential Library and Museum, FDR Papers, White House Map Room Papers (hereafter cited as Map Room Papers), box 64, “MR203(3), Sec. 1, Japanese Naval Activities, March 7–July 31, 1942.”
4. CINCPAC Dispatch 220109 April 1942, Map Room Papers, box 43, “#63—Japanese Intelligence Reports (Command 14)—2, February 19–May 9, 1942.”
5. RADM Edwin T. Layton, USN (Ret.) with Roger Pineau and John Costello, ‘And I Was There’: Pearl Harbor and Midway—Breaking the Secrets (New York: William Morrow, 1985), 390.
6. Edwin Layton and Forrest Biard both put this incident on 1 May. Samuel Eliot Morison in his History of United States Naval Operations in World War II, vol. 4, Coral Sea, Midway and Submarine Actions (Boston: Little Brown, 1949), fn. p. 22, puts it on 2 May. I go with Morison because he researched this down to the time of the sighting (1530) and whether the Japanese South Seas commander received any submarine report on his side (he did not).
7. Quoted from Morison, Coral Sea, Midway and Submarine Actions, 42.