WI: US Invades Marcus Island, no SWP Offensive

I was thinking about 3 runways with overlapping ends on shoreline, with central area of Minamitorishima dedicated for radar station and storage. The area is still enough, although the dense storage would be vulnerable by military standards and therefore costly to construct. Will need to import a lot of concrete and make a proper covered hangars and buried fuel tanks instead of blast isolation berms and above-ground fuel barrel arrays i observed on less cramped bases.
With area 1.5km2, Minamitorishima base can be ruined with about 300-500 tonnes of bombs - a quite substantial amount for Japanese capabilities of 1943

This is going to take a while. All for an exposed outpost that can't operate any serious number of airplanes. So a half-dozen B-25s could bombard Japan once a week. What happens when the battle fleet comes and shells the island? (The comments about rocket-assisted takeoffs are even more desperate attempts at justification.)

Supplying it will require convoys that will require not insubstantial escorts. As another poster put it:

To get to Marcus Island, you would have to go through Wake and the Marshalls among other places, and potentially be in range of Japanese bases in the Marianas. The Japanese may have lost the ability to go on the offensive after Midway, but they still had enough to make the US pay dearly defensively.

By 1944 when the Japanese had been ground down and the US had enough forces to launch major sustained offensive operations, there where more vital or worthwhile targets to choose from.

Granted, the attempt to take Minamitorishima can be the cause of a substantial naval battle, but more useful islands could be taken with the same amount of effort.
 

CalBear

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Can't be done. Marcus Island is a postage stamp. I'm fairly sure you couldn't park 300 B-29s on the Island

Marcus Island has a total area of just over 1/2 square mile and the MAXIMUM runway possible is ~4,500 feet. Tinian is ~39 square miles and had SIX 8,500 foot runways (which, frankly, were a bit marginal, 10K would have been better). The U.S. effort against Japan put 40,000+ personnel on Tinian (and had tens of thousands more across the Channel on Saipan, along with and additional airbase complex).
 

trurle

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This is going to take a while. All for an exposed outpost that can't operate any serious number of airplanes. So a half-dozen B-25s could bombard Japan once a week. What happens when the battle fleet comes and shells the island? (The comments about rocket-assisted takeoffs are even more desperate attempts at justification.)
High risk, high reward. Nobody says the development of Minamitorishima base to useful capacity would be easy or fast. About 6 months from capture to the first B-29 flight. In these 6 months, Minamitorishima should rely on fleet protection to avoid destruction.
Can't be done. Marcus Island is a postage stamp. I'm fairly sure you couldn't park 300 B-29s on the Island

Marcus Island has a total area of just over 1/2 square mile and the MAXIMUM runway possible is ~4,500 feet. Tinian is ~39 square miles and had SIX 8,500 foot runways (which, frankly, were a bit marginal, 10K would have been better). The U.S. effort against Japan put 40,000+ personnel on Tinian (and had tens of thousands more across the Channel on Saipan, along with and additional airbase complex).
5,500 feet with dikes extending into tidal zones. B-29 with MTOW will take-off at 4,500 feet, according to flight manual. Landing accidents ratio will be higher in Minamitorishima, but may be acceptable in wartime. The Minamitorishima was not captured mostly because of its isolation, negating part of US advantage in aircraft numbers, not because its airbase was not useful.
Regarding parking area, you can park roughly 1,500 B-29s. Realistic numbers for fully developed Minamitorishima will be around 100 heavy bombers, and 400-800 light and medium aircraft though, if you take into account taxiways, storage, radar tower, accomodations, safety gaps and AA gun nests. Military base engineer like low density layouts because it improve survivability, but high density designs do exist too, especially in area-constrained airbases (see modern Okinawa airbase for example) integrated with civilian airports. Tinian example is not very relevant here.

Given Japanese never in the war were able to concentrate more than 7 sentai of aircraft (~400 airframes) in single raid, Minamitorishima can base a non-negligible force.
 
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Can't be done. Marcus Island is a postage stamp. I'm fairly sure you couldn't park 300 B-29s on the Island

Marcus Island has a total area of just over 1/2 square mile and the MAXIMUM runway possible is ~4,500 feet. Tinian is ~39 square miles and had SIX 8,500 foot runways (which, frankly, were a bit marginal, 10K would have been better). The U.S. effort against Japan put 40,000+ personnel on Tinian (and had tens of thousands more across the Channel on Saipan, along with and additional airbase complex).
But no one's talking about flying 300 B-29s off of Marcus Island. The island can serve two main purposes:

1) It can put a small but significant number of B-24s, and later B-29s within range of the Japanese mainland. OTL, regular raids had a devastating effect on Japan's morale by proving that the military couldn't guarantee their safety. This would bring that reality home a year earlier than OTL. It's no Tinian, but it's still a substantial amount of ordinance that can be dropped on Japan on a regular basis, which completely changes the dynamic of the war going forward.

2) It can be used as a stepping stone to the Marianas and Iwo Jima, which could serve as bases for a heavy bomber offensive. If Marcus Island is captured in 1942 or the first half of 1943, then the OTL November 1943 offensive can target these other islands, and a sustained bombing offensive can start eight months earlier than OTL.

Additionally, the island can be used as a base for PBYs searching for shipping between the home islands and the southern resource area. It can also act as a FARP for submarines hunting said shipping.

Any of these purposes make it a more valuable place to capture than Cape Glouster or Peleliu.
 

CalBear

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But no one's talking about flying 300 B-29s off of Marcus Island. The island can serve two main purposes:

1) It can put a small but significant number of B-24s, and later B-29s within range of the Japanese mainland. OTL, regular raids had a devastating effect on Japan's morale by proving that the military couldn't guarantee their safety. This would bring that reality home a year earlier than OTL. It's no Tinian, but it's still a substantial amount of ordinance that can be dropped on Japan on a regular basis, which completely changes the dynamic of the war going forward.

2) It can be used as a stepping stone to the Marianas and Iwo Jima, which could serve as bases for a heavy bomber offensive. If Marcus Island is captured in 1942 or the first half of 1943, then the OTL November 1943 offensive can target these other islands, and a sustained bombing offensive can start eight months earlier than OTL.

Additionally, the island can be used as a base for PBYs searching for shipping between the home islands and the southern resource area. It can also act as a FARP for submarines hunting said shipping.

Any of these purposes make it a more valuable place to capture than Cape Glouster or Peleliu.
Only way B-24s are getting to Japan from Marcus is one way, at least with a halfway decent bomb load. B-24 combat radius with a reasonable bomb load of 4,000 pounds (range/2 then minus 30% to account for taxiway runup, take off with max load, assembly into formation after takeoff, and reasonable navigation error) is ~800 miles. Tokyo is 1,150 miles in a straight line (and, interestingly enough is also the closest part of the Home Islands) at that range the bomb load is down to around 2,500 pounds, or less.

That means 100 B-24s can carry the same tonnage as 20 B-29s The B-29 raids were more or less useless until they reached upwards of 100 aircraft. Operation Meetinghouse was 329 bombers.
 
Only way B-24s are getting to Japan from Marcus is one way, at least with a halfway decent bomb load. B-24 combat radius with a reasonable bomb load of 4,000 pounds (range/2 then minus 30% to account for taxiway runup, take off with max load, assembly into formation after takeoff, and reasonable navigation error) is ~800 miles. Tokyo is 1,150 miles in a straight line (and, interestingly enough is also the closest part of the Home Islands) at that range the bomb load is down to around 2,500 pounds, or less.

That means 100 B-24s can carry the same tonnage as 20 B-29s The B-29 raids were more or less useless until they reached upwards of 100 aircraft. Operation Meetinghouse was 329 bombers.

Here's an idea of how far it is. The red areas are economic zones of 200 miles:
Japan_Exclusive_Economic_Zones.png


The spot separated from the rest of the group is Marcus Island.

Notice that it's also surrounded on three sides by Japanese held islands. The supply convoys will have to sail far to the north to avoid air interdiction. And they will be vulnerable to submarine attacks.
 
Only way B-24s are getting to Japan from Marcus is one way, at least with a halfway decent bomb load. B-24 combat radius with a reasonable bomb load of 4,000 pounds (range/2 then minus 30% to account for taxiway runup, take off with max load, assembly into formation after takeoff, and reasonable navigation error) is ~800 miles. Tokyo is 1,150 miles in a straight line (and, interestingly enough is also the closest part of the Home Islands) at that range the bomb load is down to around 2,500 pounds, or less.

That means 100 B-24s can carry the same tonnage as 20 B-29s The B-29 raids were more or less useless until they reached upwards of 100 aircraft. Operation Meetinghouse was 329 bombers.

Lets use an actual, documented mission
In the early morning hours of August 13, 1943, twelve US B-24 Liberators from the 380th Bombardment Group (also known as the Flying Circus), began a low approach over the harbor of Balikpapan, Borneo. They were about to break records for the longest bombing run in history. Their 17-hour non-stop flight would take the Japanese completely by surprise and result in destruction in Balikpapan.

Intelligence had suggested that Balikpapan refineries were producing half of Japan’s WWII aviation fuel.

Under the command of Lt. Col. William A. Miller, a risky plan was conceived for a bombing run to Balikpapan. Pilots would need to cover 2600 miles – roughly the distance between Los Angeles and New York City.

The planes and crews were readied at the Royal Australian Air Force Base Darwin in Northern Australia. Each plane was loaded with six 500-pound bombs, 3500 gallons of fuel, and weighed nearly 66,000 pounds.
https://blog.fold3.com/the-bombing-of-balikpapan-august-13-18-1943/

Twelve B-24's of the 380th Bombardment Group took off at 5am on a bomb mission armed with six 500 lbs bombs and overloaded with fuel against the oil center at Balikpapan. Flying individually to the target, half the bombers planned to bomb the refineries and the other half would bomb shipping in Balikpapan Harbor from minimum height. Inbond to the target, the B-24s encountered three weather fronts and two B-24s aboarted the mission. Nine B-24s arrived over the target after midnight and bombed by moonlight. The sole loss on the return flight is B-24D "Shady Lady" 42-40369 force landing the morning of August 14. The returning bombers covered at total of 2,700 miles over 17 hours. References: Air Force Magazine "Valor: First at Balikpapan" by John L. Frisbee vol. 71, no. 6 June 1988.
Source: https://www.pacificwrecks.com/airfields/indonesia/manggar/missions-balikpapan.html

Range between Balikpapan and Darwin is 1232 miles, straight line, so farther away than the Tokyo-Marcus Island run. So coulds swap some fuel for more bombs, call it 3500 pounds

Upthread I listed the ground roll for a B-24 on that Balikpapan mission weight was 4650 Feet.

Sure, a B-24 isn't a B-29. That's no surprise to anyone

But what it was doing, was flying and dropping bombs in 1943 at long distances, something the B-29 could not do.
 
Perhaps B-24s could fly bombing missions to mainland Japan from Marcus Island. How many bombers could be sent at one time, and how would they fare against Japanese defenses? They would be going in without escorts.
 
Perhaps B-24s could fly bombing missions to mainland Japan from Marcus Island. How many bombers could be sent at one time, and how would they fare against Japanese defenses? They would be going in without escorts.

Basically do what Bomber Command did over Germany. No formations, individual planes bombing at night, and drop incendiaries.
By June, 1943 the design of the M69 Napalm cluster bomb was finalized, replacing the earlier magnesium based M19 Incendiary bomblets during testing on wooden style buildings expected in Japan.

Upthread I listed densities of what could be done for basing, but it's unlikely that such packed conditions would be done. With limited runways and taxiways, assembling a box formation would just take too long, so to me, would rule out precision bombing tactics as done over Europe. But as events in the Pacific with XX Command showed, USAAF wasn't married to precision daylight bombing
 
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