Invasion of Tarawa Fails

[Sea Skimmer]

Invasion of Tarawa Fails

So everyone knows the historical battle of Tarawa was a close run thing for the US Marines. Its less known that Tarawa would have been substantially more heavily defended had not US submarines sank or damaged several transports prior to the battle. Most of the Japanese troops survived those sinking’s, but all equipment was lost and the men ended up dumped on more westerly islands most of which were historically bypassed. Lets say those transports aren’t sunk, and the Japanese got enough extra men guns, concrete and staples (yeah, giant staples to hold together logs) that the Marine attack completely fails to get past the sea wall, and is wiped out by the end of the first day.

The result is 5,000 Marines killed, wounded or captured and Betio island and its airfield are still in Japanese hands. The concurrent invasions of Makin and Abermama go as historical, including the sinking of USS Liscome Bay with the loss of 644 sailors when her bomb magazine was exploded by a Japanese submarine torpedo. In all some six thousand casualties are inflicted on American forces to gain two small islands neither of which has an airfield.

So, if this were to happen. What are opinions of the long term results? Does the Central Pacific drive end before it can even get moving? Does MacArthur get to roll the US Navy under his foot? Or do we see the offensive continue, perhaps with an even greater level of bypassing then it historically had? As an even more extreme action, does Germany first really become Germany first, and additional offensive action is suspended until after the invasion of France? Keep in mind US leadership did have to answer to public opinion as well as purely military concerns, and the massive losses of the real invasion already caused the military a great deal of trouble.

[MKSheppard]

Well, the US Navy was going to have to find something to do with it's massive fleet carrier spam; but their attempt to control the PTO completely will fail, because as you pointed out, the invasion of Makin goes off as historical -- which will be a serious threat to the Navy and it's Marine Adjunct; in that the Army managed to seize and hold Makin, while the Marines simply got massacred at Tarawa.

[Sea Skimmer]

MacArthur already wanted the carrier spam to constantly support his right flank as he drove along the New Guinea Coast back to the Philippine Islands. In the Hollandia operation he historically got his wish too. At the same time historically, USS Saratgoa was sent to the Indian Ocean to support the British fleet on a couple raids on Sumatra oil facilities. I can see the inevitable push to be more roundabout in defeating Japan gaining some ground, especially because Japan had nothing like the air defenses or heavy repair capability the Germans did.

[Stuart]

My guess would be that the Marine Corps assumption of the amphibious assault role gets aborted. Amphibious assault becomes just another Army role. That has all sorts of ripples, the obvious one being that the Marine Corps doesn't get expanded and remains as a small, specialized organization mainly providing armed guards on ships and conductinga few unopposed landings now and then. Post-war the survival of the Corps is seriously in doubt and it may well not survive the 1940s. Either way, with the Army doing the amphibious role, we can be quite sure that role will get neglected by both the Army and the Navy. The Army won't train for amphibious operations and the Navy won't build the ships. By the 1960s, the institutional expertise in amphibious operations will be gone. One piece of good news, we won't have to listen to the battleship clique whining about amphibious fire support all the time.

Back to WW2. I'd guess that the Central Pacific Thrust remains more or less untouched with a few extra Army divisions replacing the Marines. The primary target is still Saipan and Guam to get the B-29s in range of Japan. However, with the Army supplying the troops, the Navy won't be in the position it was when it comes to allocating tonnage for supplies. That means that the B-29s won't be short-changed on supplies, munitions and equipment the way they were historically. That, in turn, would suggest that when Saint Curtis starts burning down Japanese cities, he won't have to stop for a couple of months when the supply of incendiaries runs out. What he will run out of is Japanese cities. That, in turn, suggests the B-29s will switch to the transportation plan earlier which accelerates the internal collapse of Japan. That may, just may, mean Japan collapses when Hiroshima gets its dose of instant sunrise without the need for Nagasaki getting the same.

[Thanas]

Would that be a net positive thing in terms of human lives lost or not?

[MKSheppard]

Post-war the survival of the Corps is seriously in doubt and it may well not survive the 1940s.

Actually, I think the real issue in the late 1940s was the fact that by 1945; the USMC had far outgrown it's original role, and had literally become "Army Junior"; competiting directly with the Army for the Land Combat Role.

BTW, this also seems to have been happening lately -- the Corps has pretty much never done an opposed landing role since ever; and is just more of "Army Junior", except with Amtracs which are rolling coffins for an entire platoon if they get hit, instead of Strykers or Bradleys.

The Army was increasingly concerned that the Navy would try to take over the Land Combat Role for itself -- with carrier borne aircraft flying over and dropping atomic bombs onto the enemy, followed up by marine divisional size landings against the nuked opposition and advancing inland behind a hail of atom bombs. So they along with the Air Force, tried to cut the Navy Department down some.

But back to WWII.

USMC Active-Duty Strength:
30 June 42: 142,613 Marines
30 June 43 - 308,523 Marines
30 June 44 - 475,604 Marines
30 June 45 - 474,680 Marines

You can see that by Tarawa, the USMC has completed a relatively major buildup of active duty marines; so this means that the Corps' role won't be entirely aborted. It will probably be held to 310,000 or 320,000 throughout 1944-45; instead of growing by 155,000 active duty personnel. Personnel who can then be re-oriented towards the Army; raising the quality of US Army divisions in both the ETO and PTO; meaning we shread the Nazis faster with less combat losses.

Either way, with the Army doing the amphibious role, we can be quite sure that role will get neglected by both the Army and the Navy. The Army won't train for amphibious operations and the Navy won't build the ships.

Well, the Army would just build the amphibious ships themselves, they've always had a pretty decent sized fleet of cargo ships et al. So it's likely that the improved LST-1171 class ships get built in smallish numbers (10-20) in the late fifties by the Army's Transportation Command.

By the 1960s, the institutional expertise in amphibious operations will be gone. One piece of good news, we won't have to listen to the battleship clique whining about amphibious fire support all the time.

I think you're overlooking a key diversion point. With no MARINES around in sufficient numbers to push OVER THE SHORE AMPHIBIOUS HELOBORNE ASSAULT (RAR!) a lot of ships don't get built.

7 x 18,400 ton LPHs (Iwo Jimas)
5 x 38,000 ton LHAs (Tarawas)
8 x 40,000 ton LHDs (Wasps)
1 x 45,000 ton LHA (America)

Each one needs 600 to 1,000 USN personnel manning them; personnel that get robbed from other parts of the Navy, not to mention the not-inconsiderable cost of building and operating the ships themselves.

In addition, each ship needs a not-inconsiderable escort screen, to ensure that they don't get sunk before the MARINES land. Without such numbers of marines floating around on the seven seas -- it's possible that the USN won't need to do FRAM I and FRAM II to simply keep up Destroyer numbers -- they just retire the old Gearings and Fletchers in the sixties, and build newer ships in smaller numbers to replace them in Carrier ASW screens.

Without MARINE OVER THE SHORE AMPHIBIOUS HELOBORNE ASSAULT (RAR!) blowing an increasingly huge hole in the USN budget from the sixties onwards, it's entirely possible that many projects which were killed to pay for Polaris or for other budgetary reasons continue onwards, like Regulus II on USN Cruisers to replace the earlier Regulus Is.

However, with the Army supplying the troops, the Navy won't be in the position it was when it comes to allocating tonnage for supplies. That means that the B-29s won't be short-changed on supplies, munitions and equipment the way they were historically.

The U.S. Army has historically always been shortchanged a lot; but they were really very innovative and forward thinking -- look at the way Marshall and other Army higher ups supported the aviators through the late 1930s and World War II -- the B-29 program alone could have paid for a US ARMY HEAVY TANK SWARM and the landing craft to carry them.

Aw, the Germans have built 1,300 Tiger Is?

Well fine, we'll deploy 5,000 M6 Heavy Tanks with three inch guns (later upgunned to 90mm) to the battlefields of Europe!

[Sea Skimmer]

Would that be a net positive thing in terms of human lives lost or not?

Likely a net gain in US lived saved, because even if nothing else changes in US strategy all, no one is going to be dumb enough to land on Peleliu, a somewhat similar very small very densely garrisoned coral island. That was probably the most useless amphibious invasion ever, and it cost the US three times as many casualties as Tarawa did. Saving 10,000 men killed or wounded on that worthless island chain easily makes up for losing 6,000 men failing at Tarawa instead of the historical loss of about 3,000 for victory. Japan meanwhile can gain nothing by keeping it, because its airfields easily could be and were suppressed by land based aircraft flying from Baik and Morotai.

Tarawa taught a very dangerous lesson to the Marines, that no matter how well defended something was if you were willing to lose a bunch of men up front you could take it in a couple days. This proved absurdly untrue at Peleliu when the battle lasted nearly two and a half months to take the place. The island is just 13 square kilometers and had 11,000 Japanese on it.

[JBG]

"The U.S. Army has historically always been shortchanged a lot; but they were really very innovative and forward thinking -- look at the way Marshall and other Army higher ups supported the aviators through the late 1930s and World War II -- the B-29 program alone could have paid for a US ARMY HEAVY TANK SWARM and the landing craft to carry them.

Aw, the Germans have built 1,300 Tiger Is?

Well fine, we'll deploy 5,000 M6 Heavy Tanks with three inch guns (later upgunned to 90mm) to the battlefields of Europe!"

Ryan, I read somewhere that the cost of 20(?) B-29s was similar to that of a new battleship, though build times were somewhat different. Does that accord with your understanding?

[Stuart]

Actually, I think the real issue in the late 1940s was the fact that by 1945; the USMC had far outgrown it's original role, and had literally become "Army Junior"; competiting directly with the Army for the Land Combat Role. BTW, this also seems to have been happening lately -- the Corps has pretty much never done an opposed landing role since ever; and is just more of "Army Junior", except with Amtracs which are rolling coffins for an entire platoon if they get hit, instead of Strykers or Bradleys.

Army-Lite would probably be more accurate than Army Junior, but fundamentally you're right. The Marines effectively became a second Army as a result of the Central Pacific thrust and ever since then they've been trying to distinguise between themselves and the other Army. More or less everything they say has been orientated to that end. Now, if that amphibious assault/rapid reaction mission goes away, so does the justification for a second Army.

I think you're overlooking a key diversion point. With no MARINES around in sufficient numbers to push OVER THE SHORE AMPHIBIOUS HELIBORNE ASSAULT (RAR!) a lot of ships don't get built. (snip)Each one needs 600 to 1,000 USN personnel manning them; personnel that get robbed from other parts of the Navy, not to mention the not-inconsiderable cost of building and operating the ships themselves. In addition, each ship needs a not-inconsiderable escort screen, to ensure that they don't get sunk before the MARINES land. Without such numbers of marines floating around on the seven seas -- it's possible that the USN won't need to do FRAM I and FRAM II to simply keep up Destroyer numbers -- they just retire the old Gearings and Fletchers in the sixties, and build newer ships in smaller numbers to replace them in Carrier ASW screens. Without MARINE OVER THE SHORE AMPHIBIOUS HELOBORNE ASSAULT (RAR!) blowing an increasingly huge hole in the USN budget from the sixties onwards, it's entirely possible that many projects which were killed to pay for Polaris or for other budgetary reasons continue onwards, like Regulus II on USN Cruisers to replace the earlier Regulus Is.

To some extent you're right although the primary budget-blower in the late 1950s through to the 1970s wasn't the marines and the amphib mission, it was the SSBN fleet and all that entailed firsta nd later the Vietnam War. Looking through the aborted projects of that era, the note that Polaris and the SSBN fleet had absorbed all the essential funding is commonplace. The numbers of escorts were also nothing to do with the amphib fleet, they were set by the perceived level of the Soviet submarine fleet. The FRAMmed Gearings and Sumners were required by the need to escort convoys over the Atlantic or so it seemed at the time. In fact, the amphibious fleet was one of the hardest-hit by the budget strangulation. The original LPD program was cut back drastically as were the LPH and LHA programs. At that time, amphibs were relatively cheap, its only in the last couple of decades that they got to be as expensive as everything else and that's due to the realization that if an amphib fuill of Marines blows up, we've just lost the war.

The U.S. Army has historically always been shortchanged a lot; but they were really very innovative and forward thinking -- look at the way Marshall and other Army higher ups supported the aviators through the late 1930s and World War II -- the B-29 program alone could have paid for a US ARMY HEAVY TANK SWARM and the landing craft to carry them.

Not so. They used different parts of the industrial infrastructure. We can switch planes for planes and tanks for tanks but planes for tanks is a no-no. The landing craft issue is a subtler version of the same thing. basically, Landing craft were built by places that more or less had nothing else to do (like PT-boats). Now, that was a deliberate and conscious decision. The landing craft were designed to use specifically those facilities with all the limitations that brought with it. (Norman Friedman goes into this in his Illustrated Design History on amphibs) One of those limitations was that they had to use materials that weren't needed elsewhere and could be handled by those facilities. That meant low-quality steel and wood and that limited the spot load to around 30 tons. That, in its turn, restricted what tanks could be handled. However, if we change that spec to give the capability of handing (say) a 45 ton tank, we are dealing with a completely different animal. It can't be built by those otherwise-unusable facilities, they have to be built by proper shipyards. So, their impact will now be on either merchant ship production or destroyer/DE production. In retrospect, the DE program could probably have been sacrificed to some extent but we know that with hindsight. It wasn't obvious at the time. That begs an important question. The amphibious assaults are not going to go away just because the Marine Corps doesn't get the job of carrying them out (its not commonly realized but the US Army actually carried out more amphibious assaults than the marines did anyway). The Central Pacific thrust will still be there, the need to invade Europe will still be there. So the amphib gear built in WW2 will still be needed.

On the supply point, the problem the USAAF had in the Marianas was that the show there was entirely Navy; the ships were Navy and the troops were Marines. So the navy had an unopposed hand in organizing supplies and transport. Guess what, the Army and AAF came a long way down the priority list, in "Mission with LeMay" Saint Curtis mentions that he saw that priority list and found the first mention of the Army and his B-29s was on Page 9. If the troops ashore are Army and the Navy is providing ships only, that changes the whole position quite dramatically.

Aw, the Germans have built 1,300 Tiger Is? Well fine, we'll deploy 5,000 M6 Heavy Tanks with three inch guns (later upgunned to 90mm) to the battlefields of Europe!

Wish t'were that easy. Here we head off into the arcane areas of industrial planning. Essentially, we couldn't land M6 heavy tanks until we'd secured a major port. That meant most of the fighting we did to secure the ports had to be carried out with 30 ton tanks and tank destroyers. The 50-ton M6 wasn't that much better than the 30-ton M4 especially once the 76mm gun was put into the M4. (Yes, the M6 had thicker armor but going from 60mm to 85mm doesn't buy much when the primary enemy gun can slam shots through 150mm of armor). So why build two lines of tanks when one represented only a marginal advance over the other yet imposed major logistical problems? There were a lot of reasons why the U.S. stuck with the M4, not the least being that it did a lot better than its critics will ever admit.

All of that, of course, is a side issue. The main problem with the Army was that amphibious assault was a side-issue to them (whereas for the marines it was the primary issue). In WW2 that didn't matter much but when budgets got tough post-war, side-issues got dropped. Side issues that needed a lot of specialized and expensive equipment got dropped very fast. So we can be very sure that the Army would have dropped any interest in amphibious operations very quickly indeed in order to rpotect funding for their primary interests, tanks, infantry and artillery. So, had the Marines remained a shp's guard - or been disbanded completely - the US would have entered the 1960s with no amphibious capability at all.

By the way, the Army operates ships for exactly the same reason that Navy operates Marines. For the Army ships, supporting Army troops is a primary mission, for navy ships supporting Army troops is a secondary mission that borders on the inconsequential. To the Navy, their Marines have amphibious assault as a primary role, for the Army amphibious assault is a secondary role that borders on the inconsequential

[Stuart]

I read somewhere that the cost of 20(?) B-29s was similar to that of a new battleship, though build times were somewhat different.

An Iowa cost around US$125 million, a B-29 around US$669,000 (which was a lot of money for an aircraft in those days). So, one could get 186 B-29s for the cost of an Iowa class BB.

[Stuart]

Would that be a net positive thing in terms of human lives lost or not?

For the allies, probably positive by a small margin. We probably wouldn't have hit Peleliu for example and might have swung straight up the ladder of the Bonins rather than diverted to the Philippines. Hard to say.

For the Japanese negative since the increased tempo of firebombing would have burned the rest of their cities down (firebombing killed more people than the atomic bombs, it just needed a lot more aircraft to do it).

[Surlethe]

Not so. They used different parts of the industrial infrastructure. We can switch planes for planes and tanks for tanks but planes for tanks is a no-no.

I don't mean to derail the thread into an arcane discussion of industrial planning, but is this because the cost of switching the infrastructure out -- production lost because of retooling factories, rebuilding production lines, etc. -- is generally considered too great a sacrifice in war mobilization? Put a different way, if the US war plan had relied significantly more heavily on St. Curtis' bomber swarms and significantly less heavily on ground warfare, how great would the benefits have to be in order to induce the military planners to temporarily sacrifice total production capacity by rebuilding tank factories into plane factories?

[MKSheppard]

In fact, the amphibious fleet was one of the hardest-hit by the budget strangulation. The original LPD program was cut back drastically as were the LPH and LHA programs. At that time, amphibs were relatively cheap, its only in the last couple of decades that they got to be as expensive as everything else and that's due to the realization that if an amphib fuill of Marines blows up, we've just lost the war.

Even with the reduced LPH program as historical (7 Iwo Jimas); that's about 4,669 men on the ships themselves, plus a not inconsequentual number on shore. Even in the sixties, the Navy was starting to experience manpower costs as the prime driver of any program, rather than the costs of the ships themselves.

That much manpower is about:

18 x Knox FFGs
or
10 x Leahy CGs

Either of which would certainly help the USN a lot more than a bunch of floating barracks for Marines.

I'm a bit pressed for time now, so I'll onwly answer that point.

[MKSheppard]

I don't mean to derail the thread into an arcane discussion of industrial planning, but is this because the cost of switching the infrastructure out -- production lost because of retooling factories, rebuilding production lines, etc. -- is generally considered too great a sacrifice in war mobilization?

Since i'm a bit pressed for time, I'll let joe baugher make my case:

There was only one P-38K-1-LO built. This prototype (42-13558) combined a P-38G-10-LO airframe with more powerful 1425 hp V-1710-75/77 (V-1710F-15) engines, rated at over 1875 hp war emergency power. The engines were housed in nacelles similar to those of the P-38J and driving broader-chord propellers. In order to accommodate the new propellers it was necessary to increase the diamater of the propeller spinners slightly, which affected the top cowling lines and the interface at the oil cooler/intercooler inlet.

Tests of the P-38K were carried out between Feb 24 and Apr 30, 1943. The performance of the P-38K was quite a bit better than that of the production P-38J--in fact its performance was superior to all other fighters then in production in the USA, including the P-51B and the P-47D. Maximum speed at 29,600 feet was 432 mph. At 40,000 feet, maximum speed was 40 mph faster than that of the P-38J. It was expected that maximum speed at war emergency power could be as high as 450 mph. Initial climb rate was 4800 feet per minute, and an altitude of 20,000 could be reached in 5 minutes. Service ceiling was expected to be above 48,000 feet, and range was expected to be increased by 10 to 15 percent. However, the War Production Board was unwilling to allow even a short production suspension in order to retool for the required changes to the engine cowling. Consequently, the P-38K was not developed any further.

[Stuart]

I don't mean to derail the thread into an arcane discussion of industrial planning, but is this because the cost of switching the infrastructure out -- production lost because of retooling factories, rebuilding production lines, etc. -- is generally considered too great a sacrifice in war mobilization? Put a different way, if the US war plan had relied significantly more heavily on St. Curtis' bomber swarms and significantly less heavily on ground warfare, how great would the benefits have to be in order to induce the military planners to temporarily sacrifice total production capacity by rebuilding tank factories into plane factories?

The answer is that it depends on the degree of the shift. Production disruption gets significantly worse as the shift from one product to another gets greater. The P-38K case Ryan mentions is a good example of a very limited shift that wouldn't have taken too long to acheive. (In passing, I have my doubts about the P-38K story, or, rather, I doubt that we're hearing the whole story. The delays involved in switching from the P-38J to the P-38K were so slight that I really doubt they were the real reason why the switch was aborted. I suspect there was something else involved that we are not hearing. Was, for example, the V-1710F-15 engine available in only limited quantities and already earmarked for another program?). Anyway, the P-38J to K shift is at the lower end of the disruption scale.

A higher level of disruption results if we want to shift types completely. If, for example, somebody wanted to shift a factory from (say) production of Hurricanes to Spitfires, the factory would have to be largely gutted and re-tooled. However, the workforce would be largely the same and require only minimal retraining. The down-time would be measured in months rather than weeks. taking things a step further, a complete change of class would result in even bigger delays. For example, changing a factory over from T-6 trainers to B-29s would probably require levelling the buildings and starting from scratch (such simple things as roofs being too low for the new aircraft or doors too small will see to that). Only a limited number of workforce skills would be transferable - workers trained to use fabric skinning on aircraft wouldn't be much use when working on metal-skinned aircraft without major retraining. Such a conversion might take a year or more and there is a serious risk that the experienced workforce would be dispersed to other plants in that time.

Looking at that progression, we can see why all the stress in wartime is on improving existing types of aircraft rather than introducing completely knew types. It seems absurd, for example, to waste time shoe-horning a new engine into an existing type and accepting compromised performance improvements when building an entirely new type around the new engine would produce a much better product. Only, the first course may delay production lines for a week or two, the second for getting on for a year. That's why the Spitfire went through 24 marks in WW2

When shifting between entirely different kinds of equipment, the delays become impossible. There is no way a shipyard can be converted to building aircraft short of levelling the place and starting again. Everything, down to the workforce and the lady who makes the tea have to be replaced. There is no level of commonality. So, while we can say that we can build one battleship or 185 B-29s for the same money the truth is that they are not competitive. The battleship uses steel, shipyards and heavy metal workers while the aircraft use aluminun/magnesium alloy, aircraft factories and skilled light metal workers. Since money isn't actually a factor in the decision (need more - print it) the choice is a battleship and the 185 B-29s. Tanks and ships are closer in general product kind but they aren't as competitive as they might seem. In another sense though, they are.

This is where life gets fun. The factories are just the end of supply chains and while they may not directly compete, they might compete for critical supplies. This is where tanks and ships conflict. During WW2 the US had enormous problems with diesel engine supplies. The same general types of diesel were used for submarines, landing craft, destroyer escorts, locomotives and tanks. So, there was a five-way balance being struck between them for diesel engine supply. It was solved this way. Diesel locomotive production more or less stopped and the older steam engines were taken out of store and put back to use. Submarines (top priority) got what they needed. That left landing craft, destroyer escorts and tanks. The DE and the tanks (the M4) were actually able to take multiple kinds of power plants. Some of the DEs got diesels, some got steam turbines, some got reciprocating engines. basically whatever was available that week. The M4 the same, there were variants that used all sorts of different engines. That left landing craft and they got what was neededdepending on whether there was a big landing coming up or not. Eventually diesel-engined tanks and DEs got cut back to free up engines for landing craft.

Armor was the same; the British cancelled their four Lion class battleships because they only had limited production capacity for armor plate. They could either allocate that capacity to producing armor for tanks or for battleships. Tanks won. Another production stream competition was in aircraft engines. PT boats used aircraft engines, so there was a specific trade-off there. more PT boats meant less aircraft.

Putting all this together meant a very delicate balancing act that was hard to get right and had to be continually fine-tuned on a daily or even hourly basis. The art was to get the maximum of fighting power out of the infrarstructure with as little wastage as possible. So it isn't really a choice of scaling back ground power in favor of more bombers; its what degree of national fighting power would be lost by scaling back ground power as compared with what increase would be achieved by using the resources freed up by that reduction for increasing aircraft production. The equation might go (in part) "well, cutting tank production by a third will free up X number of diesel engines. So, we can build more DEs or landing craft - but there's no point in doing so since they won't have the tanks to land or the landing craft convoys to escort. The engines aren't suitable for aircraft so no gain there. The armor might be useful for shipbuilding so we can accelerate cruiser and aircraft carrier production but it won't help aircraft very much. Hmm, not a good idea is it?"

[Fingolfin_Noldor]

Wait, I thought tanks had only one type of engine available? That being diesel? You mean there are alternatives?

[Mr Bean]

Wait, I thought tanks had only one type of engine available? That being diesel? You mean there are alternatives?

Shermans for example used Diesel and Gasoline engines both right up until the end of the war. There were all sorts of reports I've read about re-purposed aircraft engines being used in the first batches of shermans that were Gasoline only. And the issue with using an aircraft engine in a ground vehicle. Things like the engine was not designed to be stop/started as often as tanks where. Things like the fact that planes rarely idle thier engines for hours at a time meaning certain parts broke down quickly. I believe the most common complaint was spark plugs almost being single use only requiring replacement/cleaning at the end of every day.

[MKSheppard]

Wait, I thought tanks had only one type of engine available? That being diesel? You mean there are alternatives?

Yeeeeeees.

The M-4 Sherman was fun for this.

The original engine was a derated aircraft radial engine (it's why the Sherman's silhoulette was relatively high).

The list of engines goes as:

Continental R975 radial (Derated aircraft engine, Gasoline)
GM 6046 (2x671 inline, Diesel)
Ford GAA V8, Gasoline
Chrysler A57 5x6-cyl inline, gasoline
Caterpillar D200A radial, diesel

[Fingolfin_Noldor]

Oh wow. I forgot that aircraft engines then had a lot in common with diesel engines...

[Serafina]

Wait, I thought tanks had only one type of engine available? That being diesel? You mean there are alternatives?

Uneducated guess: Gasoline.
Not ideal (catches fire easier IIRC), but you have to use what you have got.

Very good insight into wartime economies Stuart.
How much do these things apply in peacetime?

[Simon_Jester]

Wait, I thought tanks had only one type of engine available? That being diesel? You mean there are alternatives?

In theory, you can use any source of mechanical power to drive a tank. Likewise in theory, there's nothing stopping you from using a wood-fired steam engine or a giant rubber band as a tank engine. In practice, the power-to-weight ratio would be a killer, because a tank has to carry many tons of dead weight over and above the weight of its engine and drive train: the armor and gun(s).

In practice, it boils down to gasoline, diesel, or some of the more exotic options like the gas turbine of the M1 Abrams. Diesel engines didn't start to catch on for trucks (and tanks) until the 1920s and 1930s; during the WWII era there was a lot of debate. As I understand it, one major issue with using diesel engines was that not all nations had large refineries set up to produce diesel fuel, whereas gasoline was more common.*


From a combat point of view, gasoline catches fire more easily than diesel fuel, which is a major disadvantage when your tank gets hit in a battle; gasoline-engined tanks are more likely to burst into flames, explode, and/or kill you.
_____

*Or, in light of Stuart's remarks, factories to produce diesel engines. I've been told that a lot of the diesel-fired M4A2 Shermans (about four thousand of them) wound up in Russia. I speculate that the Russians may have had either lots of diesel fuel production to drive the tanks with (lots of recent industrial infrastructure production, which would probably include diesel fuel refineries). I also speculate that the Russians' strategic equation would be simpler, because unlike the British and the Americans they didn't have to balance their land and air forces against a navy; the Soviet Navy could be pretty much put on the back burner for the duration of the war.
_____

On the supply point, the problem the USAAF had in the Marianas was that the show there was entirely Navy; the ships were Navy and the troops were Marines. So the navy had an unopposed hand in organizing supplies and transport. Guess what, the Army and AAF came a long way down the priority list, in "Mission with LeMay" Saint Curtis mentions that he saw that priority list and found the first mention of the Army and his B-29s was on Page 9. If the troops ashore are Army and the Navy is providing ships only, that changes the whole position quite dramatically.

Out of sheer curiosity, what is the name of the church in which Curtis LeMay is a saint?
Our Lady of Superior Firepower?

Wish t'were that easy. Here we head off into the arcane areas of industrial planning. Essentially, we couldn't land M6 heavy tanks until we'd secured a major port. That meant most of the fighting we did to secure the ports had to be carried out with 30 ton tanks and tank destroyers. The 50-ton M6 wasn't that much better than the 30-ton M4 especially once the 76mm gun was put into the M4. (Yes, the M6 had thicker armor but going from 60mm to 85mm doesn't buy much when the primary enemy gun can slam shots through 150mm of armor). So why build two lines of tanks when one represented only a marginal advance over the other yet imposed major logistical problems? There were a lot of reasons why the U.S. stuck with the M4, not the least being that it did a lot better than its critics will ever admit.

At a guess: I think the problem is that the reason it did so well has a lot to do with the fact that so many of them could be delivered to the theater... but giving them that advantage required making them light. Which tended to increase the already unfavorable casualties the US Army was taking against veteran German tankers. And that kind of casualty rate leaves very bad impressions on the generation of people who actually had to drive the tanks, as opposed to the (older) generation who did the strategic and industrial planning in the first place.

End-user perception has a lot more effect on popular culture than logistics calculations that even the people who did the math usually don't bother to try and publicize.

By the way, the Army operates ships for exactly the same reason that Navy operates Marines. For the Army ships, supporting Army troops is a primary mission, for navy ships supporting Army troops is a secondary mission that borders on the inconsequential. To the Navy, their Marines have amphibious assault as a primary role, for the Army amphibious assault is a secondary role that borders on the inconsequential

Though I'd think the inconsequential nature of the role has a lot to do with the Marines having already staked out that territory.

[Sea Skimmer]

The vast majority of Sherman’s had gasoline engines. The reason being that the US didn’t make that great of small diesels nor did we produce the ones we did make in anything like the required numbers. The story was different for locomotive scale diesels, which we used to power landing ships, submarines and destroyer escorts but that’d only be useful for a tank if we built something the size of P1000.

Meanwhile we did make lots of small gasoline engines, and everything else US Army already burned gasoline. Diesel fuel for medium tanks and nothing else didn’t make sense. You’d be stuck with fuel trucks hauling fuel they cannot burn themselves. The main users of the diesel Sherman’s were the Marines in the Pacific who were supported by many diesel powered watercraft. Duplex Drive Shermans were also usually diesels because the diesel was more tolerant of water being splashed into the air intake without stalling.

From a combat point of view, gasoline catches fire more easily than diesel fuel, which is a major disadvantage when your tank gets hit in a battle; gasoline-engined tanks are more likely to burst into flames, explode, and/or kill you.

Yeah and that was particularly a problem with regard to mine strikes. Shellfire was less of a concern, because it basically had to hit the crew or the ammo first before it could hit the fuel. Gasoline powered armored vehicles persisted in US service well into Vietnam War anyway. The Marine LVPT5 amtrack is notorious for this as it was the size of a small house, held 37 men internally, and had its gasoline fuel tanks under the floor for stability in the ocean. This worked out absurdly well when it hit mines coming ashore or on land.

[Stuart]

Out of sheer curiosity, what is the name of the church in which Curtis LeMay is a saint? Our Lady of Superior Firepower?

The Church Of The Immaculate Gray Lady. Saint Curtis is the patron saint of urban redevelopment

[Simon_Jester]

Meanwhile we did make lots of small gasoline engines, and everything else US Army already burned gasoline. Diesel fuel for medium tanks and nothing else didn’t make sense. You’d be stuck with fuel trucks hauling fuel they cannot burn themselves. The main users of the diesel Sherman’s were the Marines in the Pacific who were supported by many diesel powered watercraft. Duplex Drive Shermans were also usually diesels because the diesel was more tolerant of water being splashed into the air intake without stalling.

Well... that and the Lend-Lease users. As I said, about four thousand diesel-fired M4A2s (the same version the Marines used) went to Russia. Unlike us, the Russians were already committed to diesel fuel for a large chunk of their tank force, so it was less of a problem for them.

[Sea Skimmer]

Just about all the vehicles the Soviets designed were diesels. Its much easier to make an air cooled diesel engines of significant horsepower then a gasoline one, and a liquid cooled engine is a serious liability in the Russian winter. Germans found that out the hard way, especially since most of the hard worked gasoline fueled Panzers had no anti freeze in the coolant at all owing to the great difficulty of supplying it.