I'm pulling several strands of this topic, as follows; to an unusual and interesting conclusion which is only partial
vis-à-vis - 'Who transmitted, the IJN alert of 1830 (JST) on 10 March 1942; 600 naut. miles from Wake Island. ??
1 - http://www.j-aircraft.org/smf/index.php?topic=10088.0
Reply #1 - The raid on Marcus by Enterprise was not the real reason for 5th Koku Sentai's delay in reaching Staring Bay. True, Zuikaku and Shokaku sortied in an attempt to intercept the U.S. carrier, but were relieved of that duty on 7 March and left Homeland waters on the 8th, headed for Staring Bay in order to rejoin KdB.
According to 5th Koku Sentai War Diary, as cited in Senshi Sosho Vol. 26 [N.E.I. and Bay of Bengal Navy Offensive Operations] pp. 623-624, a radio intercept was received at 1830 (JST) on 10 March indicating possible enemy carrier activity 350 degrees, approx. 600 naut. miles from Wake Island. 5th Koku Sentai was ordered to pursue on the 11th. The two carriers changed course in compliance. and radioed estimated arrival 190 degrees, 120 naut. miles from South Iwo by 0600 on 13 March, with intent to advance to 50 degrees, 300 naut. miles from Iwo Jima by 1200 on the 14th. But lack of subsequent radio intercepts caused Combined Fleet to conclude that the whole thing was a false alarm. Fuel expended in this detour, however, forced 5th Koku Sentai back to Yokosuka on the 16th to refuel. It then set out next day to join KdB at Staring Bay once more.
2 - Japanese intentions to mount a major offensive into the Indian Ocean were placed on hold in March 1942; since strong naval forces were needed in the western Pacific against the United States, and the Imperial Japanese Army refused to allocate troops for an invasion of Ceylon. The IJN developed Operation C as an aggressive raid into the Indian Ocean in early April to destroy the British Eastern Fleet and disrupt British lines of communications in the Bay of Bengal in support of the Burma Campaign.
British intelligence correctly assessed the Japanese strategy. The Americans were notified; the Doolittle Raid – which was already in progress – took on the additional role as a diversion.
Admiral Isoroku Yamamoto issued the initial order to proceed with Operation C to the IJN's southern force, commanded by Admiral Nobutake Kondō, on 9 March 1942.
3 - 10 March 1942
- Eglin - Doolittle stated in his after-action report that the crews reached a "safely operational" level of training, despite several days when flying was not possible because of rain and fog. One aircraft was written off in a landing accident on 10 March and another was heavily damaged in a takeoff accident on 23 March.
The challenge of learning short field takeoffs in a short period of time had consequences. The first incident happened during a navigation flight on the afternoon of March 10, 1942. B-25B SN 40-2254 suffered nose wheel failure after landing at Ellington Field, Texas. None of the 6 men on board were injured. Pilot Richard O. Joyce had just landed and the aircraft developed a severe shimmy in the nose wheel about 400 feet from the end of the runway. Power was cut to the engines and the nose wheel collapsed. It was determined the cause was a malfunction of the shimmy dampener on the nose landing gear. The aircraft would eventually be repaired, but it would not return to Eglin during training.
4 - 8–13 March 1942
- The Invasion of Salamaua–Lae, Operation SR, was an operation by Imperial Japanese forces to occupy the Salamaua–Lae area in the Territory of New Guinea during the Pacific campaign of World War II. The Japanese invaded and occupied the location in order to construct an airfield and establish a base to cover and support the advance of Japanese forces into the eastern New Guinea and Coral Sea areas. The small Australian garrison in the area withdrew as the Japanese landed and did not contest the invasion.
10 March 1942
- In response to Japanese landings, a United States Navy aircraft carrier task force including the carriers Yorktown and Lexington struck the invading Japanese naval forces with carrier aircraft on 10 March. Supporting the carrier aircraft were eight B-17 bombers of the 435th Bombardment Squadron of the 19th Bombardment Group from Garbutt Field, Townsville, Australia and eight Royal Australian Air Force Hudson bombers of No. 32 Squadron from Port Moresby, New Guinea. The raid sank three transports and damaged several other ships. The raid sank or damaged two thirds of the invasion transports employed. Higher casualties among the Japanese Army personnel were only prevented by the fact that most of the transports had been close to shore and could beach themselves. The psychological impact was greater, putting the Japanese on notice that the Americans were willing to place their carriers at risk to oppose their moves in the region. The fear of interdiction by US carrier forces against future operations contributed to the decision by the Japanese to include fleet carriers in their later plan to invade Port Moresby, resulting in the Battle of the Coral Sea.
5 - The IJN's Indian Ocean raid (Operation C) from 31 March to 10 April 1942
, struck Allied shipping and naval bases around Ceylon, but failed to locate and destroy the British Eastern Fleet. The Eastern Fleet, commanded by Admiral Sir James Somerville, was forewarned by intelligence and sailed from its bases prior to the raid but its attempt to attack the Japanese was frustrated by poor tactical intelligence.
The British interpreted their position as precarious. Ceylon and the Eastern Fleet were required to safeguard the sea lines of communications through the Indian Ocean. The British expected the Japanese to continue threatening these lines. SIGINT suggested that the Japanese were preparing a deliberate advance across the Indian Ocean. The raid demonstrated that the RAF was too weak to defend Ceylon and the naval anchorages, and that the navy was ill-prepared to meet a Japanese carrier force.
The Eastern Fleet transferred its main base to Kilindini, Kenya, in East Africa, temporarily ceding the eastern Indian Ocean to the Japanese; from there it continued contesting control of the central Indian Ocean on better terms. Force A, including its two aircraft carriers, Indomitable and Formidable, retired to Bombay, and Somerville regularly deployed a fast carrier force to the central Indian Ocean over the next six months, during which he operated from or near Ceylon for nearly half that time. On 18 April, naval planning accorded the Eastern Fleet the highest priority for reinforcement, which also included transferring most of the carriers from the Home Fleet and the Mediterranean, with the intention of returning to Ceylon in September.
By June, Ceylon was defended by three RAF squadrons (64 aircraft, plus reserves), three strike squadrons (including one of Beauforts), and much improved radar and anti-aircraft defences. Ground defences were manned by two Australian army brigades. The invasion scare was short-lived. British intelligence detected the movement of the Japanese carrier force eastward in mid-April, and their deployment in the Pacific in mid-May. After the Battle of Midway in June, it was realized that there was no longer the threat of major Japanese naval activity in the Indian Ocean. In September, British intelligence predicted Japan would go over to the defensive. As a result, the Eastern Fleet was not reinforced as planned and, instead, shrank after early July.
12 March 1942
- IJN Aircraft Ferry [a href="https://www.wrecksite.eu/wreck.aspx?137483
"]Goshu Maru[/a] arrived at Wake Island and unloaded six type 96 Mitsubishi A5M 'Claude' fighter aircraft. speed: 17.5 knots
11 March 1942: Arrives at Wake Island. Unloads six Type 96 A5M Claude fighter aircraft.
12 March 1942: Departs Wake Island. http://www.combinedfleet.com/Goshu_t.htm
AV Goshu Maru (10,600 tons, 14.5 knots) http://pwencycl.kgbudge.com/J/a/Japanese_4_Fleet.html
Doubt about ships fate 44/45 bombed/mined.
Goshu Maru.... and [a href="https://books.google.co.uk/books?id=qOD ... 42&f=false
Joe Rochefort's War: The Odyssey of the Codebreaker Who Outwitted Yamamoto at Midway.
Gushu Maru was delivering aircraft to Wake Island. Zuikaku and Shokaku were diverted to intercept US's carriers in that area. Goshu Maru was later implicit to Rochefort's work.