JAAF vs JNAF

On another board on this site, I saw a string that eventually got down to the JNAF was better than the JAAF. Had better aircraft, pilots, training etc. and generally carried the burden through much of the war. I must admit that I once shared that view. I also am under the impression that many others have a similar opinion (that is, Navy was superior).

Because of differing tactical doctrines, I now think it becomes a bit difficult to make such comparisons in a meaningful way. However, in certain respects I find the JAAF more forward thinking and advanced than the Navy.

JAAF Army Flying Regiments were almost uniformly commanded by experienced flying officers capable of leading them in combat. To a lesser extent this was true of Flying Brigades. In the JNAF both flying officers and non-flying officers commanded Air Groups (kokutai) and seldom did the CO or even the Executive Officer actually lead the unit in combat. Especially later in the war the 'senior' flying officer was often relatively inexperienced.

Despite some USSBS statistics to the contrary, the JAAF maintained a high quality flight-training program until 1944. The JAAF did not follow the JNAF policy of putting some flight students into selected combat units to complete their training in 1943.

One might say that the IJNAF was more strategic minded - long range bombers and long range fighters gearing for fighting the USN at great distances in the Pacific.
On the other hand the JAAF was designed more as a tactical air force to support Army operations against the Russians, lots of short range, close support aircraft.

The Navy made earlier and more extensive use of cannon than the Army, which generally stuck to machineguns in its single-engined fighters until quite late in the war.

Am I to take it from your comment that you consider that in adopting the 20mm cannon the JNAF was more advanced/enlightened (?)than the JAAF. Is that the point?

Could you clarify reports (at least one) from Allied intelligence that the JAAF 12.7mm explosive round had as much explosive effect as an Oerlikon 20mm explosive round (but poor penetrative powers). Does this seem credible?

I also note that when Lt. Cdr Mitsugu Kofukuda returned to Japan after six months as hikotaicho of 204 Ku in the Solomons he wrote an extensive report with various recommendations, one of which was that the JNAF adopt the 12.7mm MG for fighters (eventually the Zero did add 12.7mm guns). The USAAF and USN did not seem embarrassed to mount 12.7mm guns.

The 12.7mm HE projectile used in the IJA's Ho-103 contained 0.8g of Penthrite wax. The 20mm HE shells used in the Navy's Type 99s contained between 5g (with tracer) and 10g (without) of Pentolite. I'll leave you to make your own judgment about which was likely to prove more effective....

The best all-round WW2 aircraft calibre was 20mm, as it combined the destructiveness of a decent HE content with reasonably light weight and high rates of fire.

The IJN was therefore more far-sighted, IMO, in adopting cannon early on. Unfortunately they chose the Oerlikon, which was one of the less impressive performers (particularly the low-velocity Type 99-1).

The IJA's 20mm Ho-5 was very good, although the ammo had to be downloaded to avoid overstressing the action as the guns increasingly had to made from poor-quality materials.

The US 12.7mm (more powerful than the Ho-103, incidentally) was OK against fighters - particularly poorly protected ones as the Japanese tended to use until late in the war - but it's just as well the USAAF/USN never had to deal with tough armoured bombers.

To be fair, the Ho-103 was also a good little gun, more compact and fast firing than the Browning M2. The IJN later adopted the more powerful 13mm Type 3 - almost a carbon copy of the M2 - but note that it was used to replace 7.7mm MGs, not the 20mm cannon.

OK, I really can't resist getting into this 20 vs. 12.7 discussion. You're missing two related major factors -- pilot attitude and required skill.

Caliber makes no difference if the pilots won't use the guns. Army pilots didn't like the 12.7's especially when synched, and Navy pilots REALLY didn't like the 99-1's. Both made most of their kills with their synched rifle-caliber guns for a long time after the heavier caliber guns were introduced. When pilots began asking for .50's, they meant US .50's, because they hated the fact that US pilots began shooting so far away. Tactical training in both services called for close-in attack, regardless of the "vision" of the people who put the bigger guns on the planes. The fighter schools were not staffed by the visionaries and even when bigger guns came, they were still not intended to extend range.

Only as tougher targets forced reliance on the heavier guns did the pilots really try to learn to use them. The greater curve of the trajectories and slower rates of fire required greater skill, especially with the 99-1. If you weren't good with the rifle-calibers, you might never get good with the heavier guns. These human factors tended to negate any technical advantage of a 20 over a 12.7

I agree with you, Ted, but that doesn't negate my basic point that the IJN were quicker than the IJA to realize the need for more destructive fighter armament. Incidentally, I don't think I said that a better long-range performance was the reason for adopting cannon; it was just the added destructiveness. (As a matter of interest, when the RAF first installed the powerful Hispano cannon in fighters they specified a harmonization distance SHORTER than that of the .303s...).

The whole question of fighter-v-fighter combat is an interesting and complex one. As you say, pilot skill was by far the most important aspect. I don't have any statistics to hand, but I believe that the great majority of kills were made by a very small minority of pilots.

Another point is that the great majority of kills seem to have been made at short range, probably 150m or less. Even the aces usually liked to get in close before firing. I recently read Saburo Sakai's book and recall a comment he made about one combat, when his unit were attacked by US fighters. He said that the Americans started shooting from long range (around 400m IIRC), which immediately told him that they were inexperienced and therefore not a serious threat.

Given the above, the trajectory of even the Type 99-1 is unlikely to have been a major issue in deciding combat outcomes. I have no doubt that the IJN pilots grumbled about the cannon (it is not uncommon in warfare for soldiers to complain that their enemy has better equipment - although I don't recall reading similar complaints from the Luftwaffe pilots in the BoB, when the Bf 109 had effectively the same armament as the Zero). However, the chances were that if they noticed a significant trajectory drop, they were probably firing at too long a range to stand much chance of hitting, whatever they were armed with.

I think that the .50 had two main advantages over the Type 99-1 (I'm ignoring here the Japanese RCMGs which were of little use later). One is that the higher velocity gave a shorter flight time which was an important advantage in deflection shooting. There is plenty of evidence that most pilots were poor judges of the aim-off required (the great majority of kills seem to have been made from directly behind), usually underestimating it substantially, and a shorter flight time minimized this problem. Incidentally, the introduction of the gyro sight in the last year or so of the war brought huge benefits.

The other advantage of the .50 was that US fighters eventually fitted six of them. The sheer volume of fire which this produced greatly improved hit probability and destructiveness. When you take into account that the .50 M2 weighed MORE than the 20mm Type 99-1, and imagine what an armament of six Type 99s would have done to a target.....I think that this was the biggest failing in the armament of the Japanese fighters. It wasn't that their guns were so much worse, just that their planes weren't sufficiently powerful to carry enough of them.

Then there is the question of trajectory. The 7.7 and T. 99-1 were a bad match as far as trajectory is concerned. The 7.7 and T. 99-2 matched very closely.

I have no doubt that 2x7.7 plus 2x20 was not only a great advance for Japanese aviation in 1940 but pretty much brought the JNAF to world standards. Then again US .50 could hit and kill a Zero at well over 500 yards. A 20mm wasn't effective until much closer, which means (in a head on or relatively safe approach) not enough firing time to inflict significant damage on a B-17 (average 20-25 for a kill).

A fighter with weapons as effective as US .50's could break off passes at 500 yards with a chance of inflicting damage while an Oerlikon fighter would not be in effective range at that distance.

I understand that as Japanese pilots said their 12.7s "have a more curved trajectory than" US .50's. Point being, not all 12.7s are the same, not all 20s are the same. You gotta work with what you have.

The Japanese Navy adopted a 20mm gun (basically a ww1 era weapon that had many good features). The Japanese Army did not. In fact only the Ki 43 mounted as much as a single 12.7mm at the outbreak of the Pac War. So in this regard, I think you are entirely right in pointing to this as an example of the JNAF being more advanced.

The armament of the Zero in 1941 was coincidentally virtually identical to that of the Bf 109E in 1940. At that time, I don't think that US fighters had the 6 x .50 armament; they usually had no more than a couple of .50 and some .30.

For a while, IJN aircraft almost stood still in armament development while the US aircraft "gunned up". The IJA kept a light armament for much of the war.

The Japanese then went in for a belated catch-up exercise and were producing some formidable 30mm and 37mm weapons by the end of the war (as well as the very good 20mm Ho-5), too late to do them any good.

I think it is easy to find points where IJA or IJN innovated before the other. Perhaps the real point should be they really did not want to share, literally so much as a rivet on a/c let alone tactics or full designs. Many people here don't agree with me I know but Japan due to Army - Navy Rivalry produced too many duplicate designs thus hampering production and resources. For instance Ki43-Zero. Zero was far better a/c and entered service much earlier in production with both Mit. and Nakajima but Army decided to went ahead with a new inferior design using the same engine.

Similarly while Army had Ki84 and Ki44 Navy developed J2M and Shinden with same mission and in the case of Shinden with the same engine with inferior performance. It would have been much productive to concentrate on fewer designs and produce them for much larger numbers for both Navy and Army. Well of course once one was assassinating the other for power struggle things like this were quite difficult to achieve, even at the expense of the Nation itself.

I think in simpler terms what IJAAF had done was innovation for Japanese but it was simply trying to catch world air forces, on the other hand what IJNAF had done was quite revolutionary and thus came the more modern reputation.

It was not only Air Forces but in general Japanese Navy was quite dynamic. They had the first 16in and 18in battleship in the world, largest submarines afloat, largest carrier force and used as main strike first in the world (I don't think Taranto attack was classified as such but it is another first). Comparing with that IJA did not even recognize the importance of machine gun and sent its soldiers to the war with rifles as tall as they are. IJA weapons were poor, they were too many different types of ammunition for different types of weapons.

(Ed. Note: this thread subsequently spun pleasantly but completely out of control, covering all sorts of weapons/engines/components topics of both Allied and Axis aircraft. Great stuff, but not all relevant to J-Aircraft.com. So I exercised what little authority I have and trimmed the thread to reflect Japanese content.)