A lot to unpack.
So, from the previous discussions it looks like it will be a surface action between the forces of Admiral's Crace and Goto that is going to determine whether or not a Japanese Landing at Port Moresby is even possible. So, let's get to the nitty gritty of it.
You ought to read my treatment of an ATL Coral Sea. It actually addresses these points.
Before beginning I am going to disclose that I am not an expert on matters of world war two surface combat so I am hoping the board will be able to provide the expertise to help determine how that action was likely to have developed and the results. In fact, I am hoping there will be several versions that can be thought up so we can explore and debate which of several possible outcomes is likely.
Point by point follows.
Now on to the setting. As per the OP, both main carrier forces will be fighting each other between May 7th and May 8th with enough damage inflicted on both that they are forced to retire and effectively are unable to influence the action that is about to take place. Also, the carrier strike that finds and sinks the Shoho prior to noon on May 7th does not occur so the invasion force and the support groups are not frightened into retiring and continue with their planned sea voyage.
ADM Inoue Shigeyoshi was the IJN expert on aircraft carrier operations.
Basically, Inoue was the mastermind of the battle plan and he was the man who lost the battle. Whereas, Takagi Takeo, was the one who blew it on the tactical level, Inoue failed to use his air-battle resources at Lae and Rabaul to cover the Shōhō end around and he assigned an idiot, Gotō, to mastermind the movement through the Jomard Passage. (See map for intended plan.)
Note the approach routes and wide separations of "Braindead Takagi" and the guy he was supposed to cover "Shipwreck" Shima Kiyohide who was supposed to take Tulagi and set up a seaplane recon base there
prior to the expected main aircraft carrier ACTION?
Fletcher bombed Shima in a shrewd pre-emptive and very risky attack that still provokes debate over American naval historians and shattered that part of the plan, so Shima is not going to join anybody. Of course he was never supposed to do so! As for "Braindead"?, well he farts around near Rabaul for a whole day trying to deliver a half dozen Zeroes and fails that mission and suddenly hears about Shima's little problem and then realizes he was supposed to cover Shima. He circles San Cristobol a whole day and a half late (refueling delay.). Meanwhile Fletcher now kills Shōhō. OOPs. Both aircraft carrier forces play out the weather front game northwest to southeast off the Solomon Islands with the result that Lexington is lost, Yorktown is dedecked, Shōkaku is dedecked and Zuikaku's air group is annihilated. BOTH carrier forces run for their lives not knowing the exact status of the other. Communications breaks down at this point and Inoue is blind and deaf at Rabaul. He more or less pieces things together and issues his first recall. (After
"King Kong" Hara Chūichi gets on the radio and lets Yamamoto know the straight dope and Inoue finally hears it.). By this time, Yamamoto is boiling mad, and he orders Inoue to proceed with the mission, and Inoue obeys, but Inoue thinks better of that order and realizes the Allies will be waiting with the works for Goto and
Kajioka Sadamichi, and orders the recall for the second time. Coral Sea RTL.
For the Japanese we have Admiral Gotō and his 4 ship heavy cruiser force supported by the Shōhō and a destroyer are positioning themselves to cover the invasion force of 1 light cruiser, 6 destroyers and 11 transports (plus miscellaneous smaller ships) as it makes its way into the Coral Sea via the Jomard Channel. The convoy is proceeding at 8 knots and will soon be joined by the covering unit of 2 light cruisers, 1 seaplane carrier and 3 gunboats that supported the Tulagi invasion operation. If all goes well the combined forces will be offshore at Port Moresby by May 10th which was also under observation by 2 imperial navy submarines.
Except that "Shipwreck" is headed for Nauru as per his orders.
Meanwhile Admiral Crace's forces of 2 heavy cruisers, 1 light cruiser and 3 destroyers on the morning of May 7th was detached from Task Force 17 and was morning of May 7th. and was rushing north and westward in order to position itself so it could engage the oncoming Japanese forces.
VADM John Gregory Crace, for all that he was a political embarrassment and did not play well with Americans, versus Gotō?; I'll take that bet and give you the odds. Gotō muffs it and the Port Moresby expedition is still recalled at the ATL Battle of Jomard Passage. Daylight battle with Americans and a good RN night or day SAG fighting tactician? Gotō is simply crushed in a pure gun action.
One more thing to consider. Even though the massive carrier air battle to the east are having no impact, both forces are being paid attention by the land based air forces of both sides. On May 6th there were several attempts by US B-17s staging out of Port Moresby to attack the Japanese forces; without any apparent success. And in the early afternoon of May 7th, Japanese aircraft from Rabaul attacked Crace's command; again with no damage but causing him some concern and an ask for air support from Admiral Fletcher (that was not granted unless you call your own air force attacking you; presumably by mistake!!!). Crace then began turning south to try and avoid any further attacks while still keeping watch for the approaching Japanese surface forces.
He stays put and waits, for that is what actually happens.
So there you have it. What happens next?
Shōhō is sunk along with
Aoba (Gotō's flagship; and he dies.);
Kako,
Kinugasa,
Furutaka are mauled with at least 1 of them scuttled, Takagi is reassigned to subs, a non-command in the IJN for that admiral with political pull (For his incompetence.), Hara is beached (as part of a coverup.), inoue is beached (for his cowardice.), Port Moresby is still in Aussie hands and Mikawa is short a few cruisers and
Savo Island NEVER HAPPENS.
It could go any one of several ways; one issue, of course, is that if the IJN transport convoy is moving slowly southwest toward Port Moresby so Marumo's task group can join steaming west (more or less) from Tulagi, they're going to be waiting for a while. Kamikawa Maru and the three "gunboats" are all converted merchant ships, so they're not exactly greyhounds. That exposes all concerned to additional Allied air attack, and/or one of the several USN submarines in the region to reposition ... and they had their successes; Okinoshima, which was Shima's flagship for Tulagi, was torpedoed and sunk on May 12 by USS S-42. Okinoshima was a large, purpose-built warship of some 4,000+ tons, so right between HMS Abdiel and HMS Adventure in size.
After Fletcher's raid on Tulagi, the
RADM Marumo Kuninorio cover force is stuck at Tulagi. Their orders are to get that seaplane base operational and this they do. It is the only part of MO that goes according to plan.
If Crace moves to the south (and by extension, Fletcher) simply wait for the situation to clarify - say by the IJN dropping anchor and starting to put troops over the side - Crace knows exactly where the Japanese are and the Japanese, presumably, don't know where he is …
Radar gun action south of Jomard in broad daylight under patchy rains with Allied air cover advantage? Chances for Gotō? < 20%. Or off Port Moresby; as if they waltz into range of the 13th FR (artillery)
QF 4.5-inch howitzers? as they try to land those high on life SNLF bravo-boys here?
or here?
The stupid shall be killed by Arty. See those hills?
Likewise, Fletcher can detach as much of his screen as he deems prudent under Kinkaid and send it northwest at high speed to join Crace. It's worth mentioning that the IJN did not have good intelligence on what the Allies had in Australian waters, and - ISTR - they thought HMS Warspite was in the theater, which may help explain why once Shokaku and Zuikaku were hors de combat historically, the Japanese didn't just bull through.
That was Inoue's excuse. Actually OOB wise, the IJN were clueless. They had no idea Yorktown was present for example, until Fletcher announced himself at Tulagi.
This could end up a lot like Savo, except the positions of the Japanese and Allies are reversed.
Agreed. I think a closer comparison is Norway 1940 where both sides play blindman's bluff, though.
I don't think you see Midway impacted - Nimitz was too good a strategist to weaken his concentration of forces for what he knew to be a decisive showdown - but I do think you are likely right that the chief impact of the Japanese taking Port Moresby would be psychological.
It could be a Midway type showdown with both sides trying for Coral Sea round 2. As I see it, (YMMV), this is what the IJN should have tried since the USN advantages are somewhat negated with both sides not being near their main naval bases and with American shore based air much weaker.
Of course this could also panic the Curtin government and the Americans to lend lease and build that Alice Springs to Darwin rail line.
Even if the Americans have just achieved some kind of success in turning back an IJN carrier force in Coral Sea, this latest setback in New Guinea would be a hard blow on top of all the other defeats over the previous six months. It would be the last Australian outpost beyond Assie shores now wiped out, nothing left but blue sea between Oz and the marching Japanese war machine. Curtin and his commanders won't appreciate fully the limited size of the force at PM, or how shoddy Japanese logistics are; or, most of all, that the Japanese are now at the outer limits of what they can reasonably seize or reasonably defend. (Nota bene: the Australian Minister of the Army at the time was Frank Forde, the MP for...northern Queensland.)
I think that would be true for MacArthur, too. BUT, the USN was acutely aware of the logistic sortie radius of the IJN and what their sustainment limits are. One of the reasons that Pearl Harbor was a surprise was that the USN knew that IJN sortie reach and it came as a shock that Kido Butai pushed it to the absolute limit. Down there in the 8th Fleet operations area, the IJN is running on fumes. That is with tanker support. One of the reasons for WATCHTOWER was the rather bold USN calculus that the IJN could not sortie more than 40% of their surface strength from ChuUk. That turns out to be about right. Each action the USN fights is against a fraction of what the IJN was on paper.
]So it's very likely that some diversion of forces is going to happen to halt Curtin's freakout. Among other things, it could well divert forces from WATCHTOWER.
Or speed WATCHTOWER up, which I think is more likely.
As I've
observed before, I actually think Port Moresby is the best move, or at least the
least bad move, for any Japanese attempt to extend their perimeter in the spring or summer of 1942 - for the reasons given above, and also simply because it's probably the only place they have any appreciable chance to take. Supplying it, of course, will be another question...
It was the ONLY move.
I think all of us on this thread suffer from the 'Monday morning quarterbacking' syndrome. We all have the benefit of 20/20 hindsight when evaluating these scenerio's. At that point in 1942 NOBODY really knew what the Japanese supply situation was and what their true logistics capability was. Hell I'm not sure the Japanese knew themselves. Too your earlier point, Once PM is captured it becomes more psychological then physical. (Perception is reality)
Already answered. The USN had wargamed this stuff for 20 years. They knew logistics to a fare thee well.
P.S. Coral Sea was a case of defective weapons, weather effects, bad timing and completely botched communications between MacArthur's clown club and the USN. It could have been a clean air-battle sweep for the Americans and Australians. Bad luck, which will also appear at Midway, is there. And that bad luck favored the IJN.