What if...the Japanese had landed troops in Hawai'i immediately after bombing Pearl?

What patrol boats? When were these modifications made? What's the range and speed of these patrol boats by the way.

It's not at all clear to me how these liners are going to carry all those landing barges and how they are going to be launched. Also a quick check showed the speed of the liners listed as 21 knots. If that was there max speed when new do they still make 21 knots? Indeed for the length of run you are assuming can they keep up the speeds required?

Which means that they will be picked up by radar well before things are shutting down. Time enough to figure out that they aren't B-17 and alert the defenses.

If the alert is given as much as half an hour before the planes show up the chance that subs or planes will inflict much in the way of damage before an engagement occurs is pretty minimall.

Maybe for a little while. But the IJN had the same faulty escort doctrine that just about everybody had early in the war. This will leave the spotter and its escorts very vulnerable. And of course escorts don't help much vs AA either.

One of the problems here is that they could be spotted and not know about it or even if they did know about it what would they do. Say radio Honolulu goes off the air 30 minutes out for the first wave. What do they do? Historically they were going to cancel the second wave. Now however you've got the battle line hanging in the wind.

And in the mean time the British have time to secure Singapore POW and company arive safely there as well. The Dutch have time to prep the oil fields and refineries for a through demolition and also shore up their defences.

 

The problem is would it be the same info? You've made quite a few changes to the time line and not a few of them would be picked up by allied intelligence. What would the reaction to those be? Hard to say at this point as you haven't given the details on the changes or when they occur.

Which probably wouldn't occur in this time line but the 3rd wave is in serious trouble.

The weather 200+ miles NE of Honolulu is not necessarily the weather the latter expects at that time. Indeed the weather that hit the KB may hit Honolulu about 10-12 hours later or a bit sooner or later or not at all. The point is the battle fleet is out their assuming that they'll get air support. If the weather takes it out they are in trouble. Furthermore they are detached from the KB and need to be about 12 hours ahead at this point and there's radio silence to observe. In the historical time line no one is commited except for some minsubs if the KB can't strike. Not true in this alternative.

Well according to:
moon calendar
There's almost a full moon and you have your CVs running at near 30 knots. I don't think they'll be that hard to see. Unless of course the weather is bad but in that case you can write off the third wave. And the bombers might come down low enough that they would be very accurate.

Plans should include the possibility of something going wrong. Yours don't. And have mulitple points where a failure or even a deviation means disaster.

1) USAAF navigators were fairly well trained. My uncle didn't have much trouble finding an airbase in Africa after flying from Brazil. All they have to do is find the islands and they can be talked in.

At least some of the bases should be in postions where the lights won't be directly observable. Indeed some of the fields may not even be covered by IJN guns.

There will be at least some leakage. However the description makes things worse than I thought of landing in rough weather. And they still have to find the carriers. If they use the radio direction finder then there's no reason the US planes can't home on the same signal.

If you have to take repeated shots you are in trouble. Silenced pistols make a fair amount of noise especially if they are automatics and or use supersonic rounds. In addition Japanese pistols were not renowned for their accuracy or take down power. Miss on the first shot, and by miss I mean don't take down your target, and the alarm has a good chance of getting out. Try doing this multiple times and you are almost sure to get a failure.

 

That may be but were there any in Marine use on Oahu on Dec.6'41 ?

Like the residents of Oahu had never heard gunfire/explosions/artillery from any of the night and day training drills and exercises that General Short ran constantly.Business as usual.

Why would Trimble suddenly "volunteer" his men for a peacetime liberty Saturdau night duty that was not needed under the level 1 alert that his supreme commander on Oahu had just ordered ? In the interests of unit moral, why would his immediate superior have allowed it ?

No doubt but the question still is, HOW LONG would it have taken for even that drastic an alarm to actually get to everyone on a sleepy peacetime Sunday Oahu morning, that needed to hear it ?

 

Just to add some perspeective to this bombardmant of Schoefield Barracks:

( Geog 366 URLs )

 

One thing about gunfire/artillery/explosions is that you get used to hearing them and where they are supposed to be. Most artillery practice was done either on Koolawea or out into the sea. So explosions on Oahu would be very rare indeed.

Just because a unit is authorized "liberty" does not mean that there is no one standing duty. It's not like at 1700 on 5 Dec. 1941 everyone just disapeared and weren't expected back until 0700 Monday morning. The military doesn't operate that way.

Liberty passes are issued and you are expected to be back on base prior to 2345 unless you had commander's authorization otherwise. Your liberty would resume the next morning after a 0700 formation. There was a curfew in effect during Dec. 1941. That means no one was allowed on the streets without authorization from 0001 to 0600.

Well that would depend on the oders of "The Commander of the Guard". I have yet to see where a Marine Corps officer leaves an order to respond to an alarm "at your leisure".

 

Sorry for the posting. I was busy composing my 3:13 reply message when you posted your 2:48 edict and I just didn'r see yours before I posted mine.

 

Once a serious firefight had broken out and it could be confirmed that Japanese troops were landing on Oahu, the rest would fall quickly into place and US Naval, Army and Air Corps personel would be alerted and called to their battle stations.

 

at at certain point you come to the conclusion

 

As I recall, the Japanese converted a bunch of WW I era destroyers to what they designated as "patrol boats". These were about 1,000 to 1,200 ton, fairly small ships. Their torpedo tubes were removed, as well as all but one or two of their original main battery guns, and about half of the original boilers, reducing their speed to around 20-22 knots. They were originally intended as convoy escorts or harbor defense vessels, but a few were adapted to launch daihatsu landing barges over the stern; this could be done while underway. In my recollection the maximum capacity was 2-4 barges, not anything like 10.

These vessels proved to be very useful to the IJN in a variety of minor, but very necessary roles, and because the IJN concentrated new construction on larger combatant vessels, there were never enough of them. The supply of suitable WW I era destroyers was, of course, very limited.

As far as the daihatsu barges are concerned, the Japanese started building the 14-meter barges in the mid-1930's, and the larger barges later, after the beginning of the war. The 14-meter barges were always in fairly short supply, and neither the IJN nor the IJA were ever able to assemble more than a handful at one time. The Kota Bahru landings, for example, were allotted just nine of them, IIRC, and most of these were quickly destroyed by the Indian Brigade defending the beach. To their embarrassment, the IJN found during the Midway invasion planning, that they didn't have enough daihatsu's to land the battalion of JNSLF troops detailed to that operation.

As for the alleged 21-knot liners, I questioned how many the Japanese actually had and never received any response; it seems Dabrob simply "forgets" to document those issues on which he has no data, ties to "reason" the question away, or simply hopes it will be overlooked in the mass of other unsupported data.

 

On patrol boats: I don't know exactly which class Dabrob is refering to. The only ships the Japanese had that were designated this in 1941 were four Shimushu class escorts. These had a full load displacement of 1080 tons with a top speed of 19 knots. They had an 8,000 nm cruising range at 16 knots. They were armed with 3 4.7" guns and depth charges. As transports they might have been able to carry 100 or 200 men at most in extremely cramped conditions.

A fast transport landing ship like the T 1 class (1800 tons FL) wasn't available in 1941. The first of these was finished in 1944. These could launch small landing craft over the stern and could carry up to 4 small Daihatsu barges. Their cargo capacity was 260 tons or 480 troops.
Given that they are about twice the size of existing partol boats in 1941 and purpose built the 100 to 200 figure for troops in the existing boats of 1941 looks about right.
Also note, these 1941 boats were not designed to launch landing craft and their modification would have taken the better part of a year to accomplish. So, it is likely if used they would be landing a few dozen troops at a time from the ship's boats.

 

This web page lists some of the old converted destroyers and links to their TROM's Japanese Patrol Boats

In my earlier post, I was working from memory and got a few of the details a bit wrong, but basically these vessels were as I described. They certainly couldn't carry 10 daihatsu's nor the number of troops Dabrob claims. Looks like it's going to be a long miserable night for the JNSLF troops.

 

Stumbled accross this little tidbit. It is purported to be a stolen, and translated, assesment of American forces in the Phillipines and Guam.

Depending on the voracity of it's author it sheds some light on how the Japanese perceived the Americans and British during 1941.

How Japan Plans To Win

 

Of the Momi class some were indeed refitted to launch Daihatsu landing craft. Those converted could carry 1 (one) Daihatsu and carried about 50 troops max. A second problem occurs with range. This class at 15 knots can make 3000 nm. This means they will require refueling enroute and possibly before making a run in for the last few hundred miles as at 20 knots plus their range will diminish by as much as 50%.
The slightly larger Wakatake class (100 more tons than the earlier Momis would be no better. Their range is equal and their size would indicate they could hold little more than the earlier ships in terms of landing craft and troops.

 

An interesting document, however, I believe it to be phony. The data about the defenses of Manila do not ring true, although I may be wrong about that. With reference to Guam, there were only something like 150 US Marines in the 1941 garrison, not 3,000, and there were no real naval facilities, nor fortresses there before the Japanese invaded. This text also makes reference to Japanese subs patrolling the West Coast of the United States and attacking US "commercial shipping"; that was most certainly NOT pre-war Japanese doctrine. The IJN planned to use it's subs almost exclusively to support fleet actions, not as commerce raiders. It does not make sense that the Japanese Navy would publish a "book" about it's military plans and then allow Japanese Army officers to leave such a book in a hotel room. It's unlikely the IJN would even tell the IJA what it intended to do in case of war with the US. The Japanese Naval General Staff didn't even have a full time intelligence officer (let alone staff section) until just before the war started in 1941, and it certainly didn't exchange naval intelligence information with the Japanese Foreign Ministry, so the introductory information is immediately suspect.

 

That's pretty much where I am with it as well, which is why I included the disclaimer as to the voracity of the author.

Brad

 

According to the Combined Fleet page, the converted Momi class patrol boats could carry TWO daihatsu landing craft, and 150 troops, but could only make 18 knots. I can't find any record of Wakatake class destroyers being converted to carry troops or daihatsu landing craft. Apparently, there was only one Wakatake class destroyer (ex-Yugao) converted to an ASW patrol boat (PB-46).

 

Warships of the Imperial Japanese Navy 1863 - 1945 Jentschura et. al. Notes on the Momi class that 32 to 39 (renamed from the original) were rebuilt in 1941 with a stern ramp for launching a single Daihatsu landing craft. Armament was reduced to 2 4.7" guns (from 3) and the plant reduced to 12000 shp = 18kts.

I pointed out the Wakatake class, which as you note only Yugao was converted to a patrol boat 2x 4.7" (vice 3) and 60 DC 10,000 shp = 18 kts, just for completeness in case it was mentioned in the alternative as being converted to give more fast transports.

In both classes there is a lack of range necessary to make the trip without enroute refueling. Neither is capable of making 20 knots and likely neither could have sustained 18 for much more than a few hours at most in top condition. The run in using either would have more likely had to be made at 14 to 16 knots at most giving about a 13 to 14 hour transit time for the final 200 nm. This would have translated into almost certainly being spotted by the US patrol aircraft, even as sparse as they were.

 

So does this mean we have officially beaten this topic to death and can we also agree that it is "Not Plausible" for the Japanese to have mounted a successful invasion of the Island of Oahu?