Oil and Japanese Strategy in the Solomons: A Postulate


One of the most frequently-asked questions brought up for discussion by readers of my website, and contributors to some of the World War II newsgroups I read, has been (roughly paraphrased), 'Why the heck didn't the Japanese send their battleships down to Guadalcanal and put Henderson Field out of business for good?'

It's a good question. Additional Japanese capital ships clearly would have been useful in two ways:

Battleships could help establish naval dominance in the Guadalcanal area by providing a crucial superiority in surface firepower over Allied forces who did not (yet) have a comparable number of capital vessels available to them in the Pacific. Night surface actions were fairly common in the Solomons campaign. Japanese battleships, had they been present, clearly could have been decisive in a number of these surface confrontations.
Battleships also could provide the sort of heavy gunfire support necessary to neutralize Henderson field. Indeed, given the clear (if temporary) success registered after 'The Bombardment' (as the U.S. Marines referred to it) conducted by the Japanese battleships Haruna and Kongo against Henderson Field on the night of October 13-14, it is difficult to argue the point.

The traditional answers to the question of Japanese capital unit commitments have been along two main lines. The first explanation, which I would term 'the conventional wisdom', hinges on the potency of airpower. Battleships, so the argument goes, are impotent in the face of airpower. Further, one does not risk one's battleships, unsupported, unless one has air superiority over the water in which they will be operating. Therefore, given the menace that Henderson Field's aircraft posed during daylight hours, the Japanese would have been crazy to have risked their capital units in such a threat environment. The loss of the fast battleship Hiei to aircraft from Henderson Field merely punctuates the point.

This answer is unsatisfying in several major respects. First, the Japanese eventually did risk their BBs in the waters off of Guadalcanal after they had become convinced of the necessity of doing so. Certainly they might have done the same in August or September had the need, or the opportunity for decisive action utilizing capital units, been as acutely perceived. Further, the loss of the Hiei on November 14th does not negate two key facts: First, Kongo and Haruna had practically flattened the airfield just a few weeks before, and nearly put it out of business. And second, with regards to Hiei's loss, Henderson Field's aircraft did nothing more than pick off a battleship that had been crippled the night before by U.S. naval vessels. Without the sacrifice of Admiral Callaghan's squadron, Hiei would not have been waiting around on the morning of the 14th to be sunk. Indeed, the stage had been set the night before for a repeat of 'The Bombardment', which might well have left Henderson Field a smoking shambles again. Thus, while Henderson Field could confirm American naval victories, it could not create them. And without an American naval presence in the area, it stood in danger of neutralization, either through direct bombardment, or aircraft attrition.

When viewed in this light, it is clear that the 'threat environment' cut both ways. While being 'unsinkable', Henderson Field did have vulnerabilities, particularly to the large-caliber incendiary AA/bombardment shells (Type "San Shiki") that all Japanese battleships carried. Thus, the 'conventional wisdom' does not adequately explain why the Japanese failed to commit their main battle units (Yamato and Musashi in particular, but also the other slower BBs of the First Fleet, principally Nagato and Mutsu) when the campaign was younger, the threat environment much less dangerous, and the opportunity existed to destroy the fledgling American airfield and establish naval dominance in the area. At the very least, Japanese capital ships, if consistently employed earlier in the campaign, had the potential to keep Henderson Field in a near-permament state of degraded capability. This, in turn, would have made resupplying the Japanese forces on the island much easier to accomplish.

A more plausible explanation for why Japan withheld its heavy battle units centers on the failure of its naval doctrine. The Imperial Navy was built around the concept of fighting a 'Decisive Battle' against the U.S. Navy, in which Japanese battleships featured prominently. And, put simply, Guadalcanal did not fit the Japanese Navy's 'mental image' of what the Decisive Battle was supposed to look like. Consequently, the Japanese refused to release the traditional arm of decision (the battleships of the First Fleet) for duty in the Solomons, because one does not risk capital vessels in support of objectives which are not thought to be strategically decisive.

This second answer, which has been well-documented in the literature, is extremely persuasive. However, there are a number of inconsistencies with the 'doctrinal explanation' which are intriguing. Since the late 1800s, Japanese naval doctrine had been built around the cardinal principle that capital vessels were to withheld until such time as their presence was absolutely required in order to secure the strategic advantage. According to Japanese doctrine (as summarized by H.P. Willmott) "The [battle fleet] was husbanded most carefully. The cornerstone of Japanese strategy in both wars was to preserve the battle fleet and use it only if and when its commitment was unavoidable. In the Russo-Japanese war the battle fleet was committed en masse only against the last despairing effort of the [Russian] Baltic Fleet... This concept was the linchpin of Japanese strategy in the interwar period and it was what the Imperial Navy sought desperately in the period 1942-1944. The active role of the battle fleet was limited, the main effort at sea devolving on light and expendable forces operating in the forward areas. The task of these forces was either to contain or defeat the enemy, or to inflict disproportionately heavy losses if containment or defeat proved impossible."

However, even before the Guadalcanal campaign began, Japan had already demonstrated that it was willing to dissipate (some would say 'fritter away') its 'strategic reserve' (be they battleships or aircraft carriers) in pursuit of non-strategic objectives. For example, the commitment of carriers Zuikaku and Shokaku to the Port Moresby Operation (which precipitated the Battle of Coral Sea) critically dispersed the mass of Japan's First Carrier Fleet (Kido Butai) before the Midway Operation, and did so in pursuit of objectives which were clearly not strategically vital. By the same token, the Midway Operation (which must go down in history as a paragon of disregard for the principles of both economy of force and critical mass) parceled out the IJN's carriers and battleships into no fewer than three different groups (First Carrier Strike Force, Northern Force, and Main Body), only one of which was directly attacking a strategic objective, and all of which were mutually non-supportive. Thus, the argument that the IJN was attempting, per its doctrine, to preserve a 'critical mass' of battleships for some future 'Decisive Battle' must contend with the fact that the IJN had already flouted its own doctrine on several occasions during the war. At which point, one may reasonably ask, "Well, then, why stop there?"

Given the inability of the above arguments to completely explain the Japanese decision (or indecision) regarding their capital ship deployments in the Solomons, I would like to postulate the existence of an additional critical factor in the Japanese strategy-making process in mid- to late-1942. This factor contributed to a Japanese inability to perceive that Guadalcanal was, in fact, the 'Decisive Campaign' of the Pacific War, and therefore worthy of commitment of their heavy units. This factor may not have been decisive in formulating Japanese strategy, but it retarded the Japanese ability to perceive the situation clearly, and led them to fatally withhold their capital units until it was too late for 'the heavies' to affect the course of the campaign. This factor, I believe, was oil.

What follows is an examination of the logistical factors operating against the Japanese in the Solomons, and their possible interaction (and interference) with Japanese strategy formulation. What I am attempting to do is build a 'ground-up' circumstantial case for the importance of oil in Japanese thinking during this critical time during the war. While I do not have access to Japanese documents explicitly naming petroleum as a factor in the Solomons, I believe the case presented will at least pass the test of 'common sense'. If I, an amateur historian, can build a relatively straight-forward logistical argument regarding the importance of oil in Solomons, then certainly members of the Imperial Naval Staff could (and did) do so as well. The results obtained, I believe, cannot help but have been the subject of discussion during the staff meetings at Rabaul, Truk, and Imperial Headquarters which decided strategy in the Solomons campaign. I am open to comments, and welcome any additional information on this topic my readers can share with me.

Overview: Ships...

Allright, before we can kick this exercise off, we need to examine how the Japanese Navy used its petroleum products. I am going to restrict my remarks largely to fuel oil (although I have developed some figures regarding aviation fuel usage as well). In any case, we need to understand how ships use fuel, and how that relates to the scope of naval activities that the Japanese could contemplate in the region.

An examination of the available reference literature produces the following general picture of the rates at which Imperial Japanese Navy vessels consumed fuel.

Ship Fuel Usage at Cruising Speed (tons/hour)
Battleship 8 - 16
Fleet Aircraft Carrier 6.5 - 13
Light Carrier 3.5 - 6
Heavy Cruiser 3.5 - 5.5
Light Cruiser 1 - 2
Destroyer 1.5 - 2

Some comments are in order here. First, 'cruising speed' is roughly 15-16 knots. Second, bigger ships, in general, are more fuel efficient (ton for ton) than smaller ships. Third, older ships generally have less efficient propulsion plants, and therefore higher fuel usage ton-per-ton. The combination of these two factors may help explain why the battleships Ise and Hyuga, which displaced approximately 33,000 tons less at full load than Yamato and Musashi, apparently had higher hourly burn rates -- 16 vs. 14 tons/hour at 16 knots. So, too, for that matter, did Nagato and Mutsu, which were the likeliest candidates for deployment to Guadalcanal in lieu of Yamato and her sister (Ise and Hyuga were being retrofitted to battleship/carriers during the Guadalcanal campaign, and Fuso and Yamashiro were too old and slow to be contemplated for deployment in such dangerous waters.) Third, it should be noted that fuel consumption is directly related to how well-maintained the ship's power plant was, as well as the cleanness of her hull, and the quality of her fuel.

Now let's take a look at what happens when ships move away from cruising speed and maneuver at battle speed. Two examples illustrate the point. Battleship Yamato had power settings as follows:

Power Output Speed Attained
20% 16.47 knots
40% 23.20 knots
60% 25.60 knots
80% 26.60 knots
100% 27.46 knots

(Graph created using CurveExpert 1.3)

In other words, Yamato can cruise along comfortably on 20% power, but to operate at a decent battle speed she needs to be putting out at least 60% power. In actual combat operations, however, she would most likely operate at 100% power while steaming at a slightly lower speed (such as 26 knots) in order to retain a reserve for powering her weapons, fire-control systems, pumps and so on. Thus, any combat situation will likely increase Yamato's fuel usage by a factor of five over cruising speed. And, as mentioned before, Yamato was a relatively efficient vessel as IJN ships go, because she was huge, relatively new, and (as the flagship of Combined Fleet) presumably well-maintained. The ships that really feel the pain during combat operations are destroyers. For example, let's look at typical Japanese fleet destroyer (in this case, a Hatsuharu-class DD), whose fuel load is 500 tons:

Speed Radius Hours of Endurance Tons of Oil Burned/ Hour
15 knots 6000 nm 400 1.25
34 knots 1020 nm 30 16.67

That's right, the destroyer's fuel consumption increases by more than thirteen-fold at top speed! Destroyers powerplants aren't optimized for cruising; they are built for high speed and quick maneuvering, and as a result they really guzzle the fuel. This is also why 'Tin Cans' are forever topping off their tanks at any opportunity, because if a combat situation develops you don't know when you'll be able to gas up again, and destroyers can run out of gas in a hurry.

...And Oil

Next, let's examine Japan's situation with respect to petroleum production at this stage in the war. In the fourth quarter of 1942, Japanese oil production (which was almost entirely concentrated in her conquered territories, such as the Indies) was 1,194,000 tons. Of that, only 643,000 tons made it to Japan (which is where practically all the refineries were), the rest being either lost to attack, or consumed in the conquered territories. So roughly 214,000 tons of oil per month was making it to Japan. However, the Imperial Navy alone was consuming about 305,000 tons of heavy oil (in the form of fuel oil) per month by this stage in the war (Parillo, p. 237). Keep that figure in mind: 305,000 tons.

Furthermore, by this time (October-November 1942) it must have been begining to become clear to the Japanese that the oilfields in Java and Sumatra were not going to be brought back into production at nearly the rate that pre-war estimates had counted on. The Dutch and their Allies had done a much more thorough job of demolition in the oilfields than the Japanese had hoped. This, coupled with the sinking of a transport filled with equipment and valuable refinery personnel, meant that Japanese efforts to get the production field back into production were doomed to be much slower than hoped by the Japanese military. The fact that the Imperial Navy had built up large stocks of petroleum before the was could not compensate for this sobering knowledge, especially given the high rate of fuel consumption thus far in the war. The week-long Battle of Midway alone had consumed more fuel than the Japanese Navy had ever used before in an entire year of peacetime operations (Willmott, "The Barrier and the Javelin"). With this in mind, let us examine what it took to fight effectively around Guadalcanal.


At this point, it's appropriate to construct some scenarios illustrating Japanese petroleum consumption during the Solomons campaign.

Scenario One: 'The Bombardment' Redux

On the night of October 13-14, the battleships Haruna and Kongo subjected Henderson Field to one of the most intense naval bombardments of the entire war. Without question, this was one of the more succesful naval forays the Japanese made into the waters of IronBottom Sound. When the Americans emerged the next morning, Henderson Field was wrecked, most of its aircraft destroyed, and much of the stock of aviation fuel gone up in smoke. Many Americans remember this as the most desperate phase of the entire battle. With Henderson temporarily out of action, the Marines could do little except watch helplessly as the Japanese landed troops further up the coast during the morning. Frantic searching managed to turn up enough fuel to get a few aircraft flying, but it seemed likely that the days were gone when Henderson Field could dominate the seas around Guadalcanal. The sense of American isolation at this time was quite acute, and had an immediate negative effect on American morale.

But what was the cost to the Japanese in terms of their petroleum reserves? Let's examine this operation from a logistical standpoint. To perform the mission, the Japanese brought the two battleships (Haruna and Kongo), a light cruiser (Isuzu), and nine destroyers down from Rabaul. From Rabaul to Guadalcanal is approximately 650 miles as the crow flies. For our purposes, we'll call it 800 miles each way (to allow for geography, zig-zagging to avoid submarines, and so on). Japanese practice was to cruise down the Slot at normal cruising speed (call it 16 knots), and then dash in under cover of darkness. Thus, one might have a 'mission profile' looking something like this: 650 miles at 16 knots, and then a 150 mile dash in the late afternoon into the combat area at a speed of 25 knots. This would be followed by an hour-long bombardment, or naval combat, and then a similar dash back out so as to be well away from Henderson Field by morning. In addition, we will add in the fuel needed to maneuver at high speed for an additional hour, which will replicate a submarine scare, air attack, or similar combat event as the force cruises down The Slot. Base fuel consumption for these vessels is as follows:

Ship Tons of Oil Burned / Hour (16 kts.)
Kongo-class BB 9.25 (est.)
Isuzu-class CL 3 (est.)
DD 1.35 (est.)

For the purposes of our model (and throughout this essay) we will assume that fuel consumption will triple at 25 knots. In combat operations, fuel consumption will increase by a factor of five for the larger ships (cruisers and above), and by a factor of ten for destroyers. These are rough figures, but they serve to illustrate the point. When matched against the 'mission profile', fuel consumption looks as follows:

Event Speed Total Miles Traveled (nm) Total Hours Traveled Tons of Oil Burned/ Hour Total Tons of Oil Burned
Cruising Operations 16 knots 1300 81.25 34 2734
Run In/Out of IronBottom 25 knots 300 12 101 1211
Combat 30 knots 60 168 2 336
Totals - 1660 95 - 4,282

Thus, one 4-day mission consumes over 4,000 tons of oil. That equates to roughly 1.4% of Japan's total monthly consumption of 305,000 tons. 1.4% may not seem like a lot, but remember, that 305,000 tons has to power the entire Japanese Navy. That includes Combined Fleet, all of its combat units, all of it's submarines, all the training exercises, all the patrol boats out on routine operations, escorts for convoys: everything. And just wait, it gets worse...

Scenario Two: 'The Bombardment' Deluxe

Next, let's take a look at another favorite scenario: Yamamoto gets serious and brings Yamato et. al. down from Truk to put Henderson Field out of business. In fact, Yamamoto purposed to do this at at least one point in the campaign, but was overruled by Imperial Headquarters (Agawa, "The Reluctant Admiral", pp. 328-329). The reason? Apparently, the fuel reserves at Kure, one of Japan's most important naval bases (and therefore presumably a bellwether for the supply situation of the Navy as a whole) had slipped to 65,000 tons. Navy consumption of fuel had recently topped 10,000 tons a day (which jibes nicely with the 305,000 tons/month figure I arrived at independently from other sources). This explicitly points to the importance of fuel in the Solomons campaign, and indicates that in this one instance at least the IJN could not afford to commit its heavy units because of fuel constraints.

It should be noted, too, that

In any case, had Yamamoto proceeded with such an operation, his task force would probably also have included Musashi, as well as the usual contingent of cruisers and DDs. I'm going to postulate a task force composed of Yamato, Musashi, four Myoko-class heavy cruisers, a Nagara-class light cruiser, and her attendant flotilla of, say, nine destroyers -- a powerful shore bombardment force with plenty of anti-surface power. Their individual fuel consumptions at 16 knots look like this:

Ship Tons of Oil Burned/ Hour
Yamato 14
Myoko-class CA 5
Nagara-class CL 3 (est.)
DD 1.35 (est.)

Of course, Truk is a lot further away from Guadalcanal than Rabaul: 1,400 miles one way. Again, I will tack on an additional 25% (for a total of 1,750 miles) to account for zig-zagging and all that. So, our mission profile will be: cruise at 16 knots for 1,600 miles, followed by a 150-mile run in at 25 knots, followed by the bombardment and the run back out, and then the cruise home. Again, we'll also assume an air attack on the task force, and some high-speed running around in IronBottom as well, for a total of 2 hours worth of high-speed maneuvering. The fuel consumption rates for this mission look like this:

Event Speed Miles Traveled (nm) Hours Traveled Tons of Oil Burned/ Hour Total Tons of Oil Burned
Totals - 3560 214 - 15,535

Again, knowing what we know about Japanese petroleum usage rates, we have just consumed 5.1% of the IJN's monthly allowance. Was it worth it? You'd better hope so, and you'd better be prepared to repeat the exercise, because airfields have a tendency to repair themselves. This points to one of the frustrating aspects of the Guadalcanal campaign from the Japanese perspective -- decisive results didn't seem to be achievable. Rather, the campaign was one of prolonged attrition. As Admiral Ugaki noted in his diary, "It's infuriating -- we shoot them down and we shoot them down, but they only send in more." (Agawa, p. 326). From a naval perspective this meant that a one-shot attack against Henderson was probably not going to get the job done. Rather, if the Japanese were truly committed to bombarding the island airfield out of business, they needed to be able to mount such operations on a sustained basis. It might take weeks of such activity before the airfield was either eliminated or captured by ground forces. Imperial Naval HQ's refusal to send Yamato and consorts on such a mission to IronBottom Sound may have been an admission of this fact. One such bombardment mission in isolation, while possible, wasn't going to be sufficient in and of itself to secure victory. And the fuel for committing heavy units to Guadalcanal, night after night, doesn't seem to have been available.

Scenario Three: The Tokyo Express

By the mid-point of the Guadalcanal campaign, the only way the Japanese could get any troops or supplies into Guadalcanal was via destroyer -- the 'Tokyo Express.' Let's take a look at what it took to keep the Express running. Typically, the Express would consist of four to six destroyers acting as transports, and another pair acting as escorts, for a total of six to eight DDs. A typical 'transport' destroyer would be able to carry either 150-200 troops or 200 55-gallon drums worth of supplies. According to our standard 'mission profile', total fuel usage for an individual destroyer under such conditions would be 172 tons round trip. Thus, a 'typical' Tokyo Express run could be expected to consume roughly 1,374 tons of oil fuel. That's nearly 1.5 tons of oil per man or barrel (counting the amortized fuel for the 2 escort DDs) delivered to Tassafaronga Point! A ton and a half of oil, for a couple hundred pounds of rice, or one half-starved infantryman without heavy equipment, is a lamentable exchange by any standard.

Such runs occurred as often as every three or four days. Postulate a month in which six large (6 'transports' + 2 escorts = 8 DDs) Express runs occurred, bringing in roughly 7,000 men or supply barrels. It takes about 8,250 tons of oil to get that done. Congratulations! You have just consumed roughly 2.7% of the Imperial Navy's monthly oil supply to put a scant regiment of troops (4000 guys) and their rice and miso soup (3,000 or so barrels worth) on Guadalcanal! That's a lot of oil, for very little in the way of credible logistical result, because of course destroyers were manifestly incapable of bringing in the sorts of heavy weapons and equipment which were necessary for the Japanese to eject the heavily dug-in Americans around Henderson Field.

Scenario Four: The Tokyo Express ad absurdum

But in fact, by November 1942, the needs on Guadalcanal were much greater. The Japanese 17th Army's staff calculated its supply needs as being five destroyer loads per night, or 150 loads per month. Including, say, two escorts for each 5-load run (7 DDs total), that's 1,200 tons of oil per night, or more than 36,000 tons per month! And again, this doesn't begin to bring in the heavy equipment. To do that, 17th Army calculated that they would need 800 destroyer runs, as well as 20 runs from seaplane tenders. The destroyers alone (even if they had been available, which they were not) would have consumed 137,000+ tons of oil to do that job. Throw in the seaplane tenders (which were fuel hogs -- worse than a heavy cruiser), and the total fuel needed tops 150,000 tons, or nearly 50% of the IJN's monthly fuel allotment. When presented with 17th Army's plans, Yamamoto remarked that they were so unrealistic that success might be unattainable with such brains in charge of the Imperial Army's forces on Guadalcanal (Frank, p. 408). Clearly, the Tokyo Express was not getting the job done over the long haul.


The solution to Japan's dilemna, of course, was embodied in neither battleships nor the sleek destroyers of the Tokyo Express, but rather in the chunky hulls of humble cargo ships. 100 tons of fuel oil and a single decent-sized (12,000 ton deadweight) freighter will deliver a battalion of troops, and a good chunk of their supplies, too. Instead of the absurd number of destroyer loads outlined above, 17th Army's needs could have been met with 50 cargo-ship loads of troops and supplies. In fact, in terms of tonnage delivered for a given amount of oil burned, a cargo ship is something like 30 times as efficient as a destroyer. However, in order to use the plodding cargo vessels, the Japanese needed to neutralize American air power. Yet without the supplies and heavy weapons such ships could deliver, the Japanese ground forces were incapable of capturing the airfield. Quite a vicious Catch-22 indeed.

This dilemna, coupled with the perceived need to hold Guadalcanal at all costs, led to an even more ominous strategic situation. Japan had started the war severely disadvantaged in the area of petroleum stocks. If the Japanese were to win, they would have to make a virtue of necessity and fight effectively 'on the cheap' against their larger, more powerful opponent. Japanese doctrine acknowledged this inferiority, and sought to remedy the situation with an emphasis on moral superiority, training, and the usage of powerfully armed light forces to compensate for its disadvantage in numbers of expensive, gas-guzzling capital ships. In the Japanese Army, extreme aggressiveness, forced marching, and bicycles, were seen as replacements for petroleum-powered motorized transport and armored forces.

American airpower on Guadalcanal stood this Japanese doctrine on its head, at least with respect to the Imperial Navy. Henderson Field forced the Japanese to expend much larger quantities of fuel than they wanted. Further, this fuel was used to place very valuable (and vulnerable) fleet destroyers in an exposed forward position while delivering an insufficient quantity of men and supplies to the American meatgrinder on the island. The Japanese were, in effect, being forced to fight as uneconomical a campaign as could possibly be imagined, while their incomparably better-supplied opponent enjoyed all the benefits inherent in using large, efficient merchantmen. The American theater commander, Admiral Halsey, could afford to throw every ship under his command into the fray around the island, and he did so without hesitation, up to and including his own very valuable battleships. The Japanese, who certainly took the backseat to no one when it came tenacity in combat, just as clearly could not back their grim determination with commensurate fuel reserves. In the end, Japan's inability to sustain the voracious fuel needs of her warships meant that those warships could not make a sustained effort against Henderson Field or the U.S. Navy. The bitter irony of this situation cannot have been lost on Combined Fleet's logisticians.

Appendix: Calculating Fuel Consumption

My basic approach was to divide the combat radius of the vessel by the stated speed for that radius to get an endurance figure measured in hours. The amount of fuel oil carried by the ship is then divided by the endurance to give tons burned per hour at at the given speed. There are, however, a number of problems with using this approach:

First, information on combat endurance for Japanese vessels is generally spotty. In many cases, radii are only given for one speed for a given ship class. This leads to problems in estimating fuel consumption at higher (or lower speeds), since consumption rises in a non-linear fashion as speed increases. The only information I have for constructing such a power curve is for the battleship Yamato, which gives power ratings for five different speeds.

Second, many of the radii quoted in the literature are for differing speeds, making apples-to-apples comparisons of fuel consumption at a given speed a matter of educated guesswork.
Third, some of the radii quoted in the literature are clearly wrong. A striking example is the data given for the battleships Fuso and Yamashiro. In every source work I (or my associates) examined, including Japanese, the combat radius of these ships after their reconstruction is cited as being between 11,000 and 11,800 (!) nautical miles, on bunkerage of between 5,019 and 5,100 tons. If true, Fuso and Yamashiro would have been the most fuel efficient vessels in the Japanese Navy by far, this despite the fact that they were the oldest capital ships in the Navy, were more than 30,000 tons lighter than Yamato, and by the time of the Battle of Leyte Gulf their propulsion plants had deteriorated to the point where they were incapable of making more than 21-22 knots. Clearly, these vessels were far from paragons of engineering perfection, and therefore their printed combat radius must be viewed with a healthy skepticism. Either their radius was smaller, or their bunkerage was bigger, or both.
Fourth, for later-war vessels (such as the Yugumo and Matsu-class DDs), there are no available figures for bunker tonnage, making computation of a fuel consumption rate impossible, though we may have a sense for the vessel's radius.
Fifth, the figures in the literature are nominal ranges, which in most cases were theoretical, 'design-estimate' numbers based on clean hulls, proper fuel, and a well-functioning powerplant. During the course of the Solomons campaign, it is known that many Japanese vessels were operating with deferred or improperly performed maintenance, which would have degraded their efficiency. Thus, the combat-radius figures cited in the literature were almost certainly never attained under actual operating conditions.

I note, too, that the figures for fuel consumption I arrived at are universally higher than the figures quoted for both Allied and Japanese naval vessels by James Dunnigan and Albert Nofi's book "Victory at Sea." Having contacted Dunnagin and Nofi regarding their sources, I was told that they had used Conway's materials. I regret that I have not seen the Conway's figures. However, my figures for capital vessels (at the least) are the result of examining several different source works which specialize in the Japanese Navy, and I believe them to be as accurate as possible in the Western literature. Further, in the case of Japanese battleships, the Japanese literature also agrees with my figures. I am at a loss, therefore, to explain the apparent discrepencies between my results and Dunnagin & Nofi.

My thanks go to Jim O'Neil for contributing additional fuel usage figures from his reference collection.