The dive bomber is one of the most misunderstood concepts in military aviation. James Kightly explores the history and myths, and some of the facts behind the brief glory days of this specialist combat role.
The dive bomber concept had a brief heyday in the early peaks of the European and Pacific wars between 1940 and 1942, first in Axis and then in Allied hands. The subsequent swift decline of the concept caused a huge amount of mythologizing and misinterpretation.
At the time, they were the best weapon for the task. But later they acquired a reputation informed by partial hindsight: and that reputation has obscured how critical dive bombers were at the time. What did they achieve? How useful were they? First we should examine the history.
Idea to execution
The concept of the dive bomber grew out of two Great War experiences. The first (often overlooked) is the idea of pointing the whole aircraft at the target, a concept which prompted the development of the fighter aircraft as we understand it. Late in W.W.I, when undertaking interdiction and trench strafing, fighter pilots found that pointing their entire aircraft at the target while in a shallow dive achieved accuracy with light bombs and (obviously) their fixed machine guns.
In 1918, the British explored the idea of full-on high-angle dive bombing at Orford Ness, but it was dropped and forgotten with the focus on peace after a war that was supposed to end all wars.
It is believed the first combat dive bombing attack took place in early 1919 when a United States Marine Corps (USMC) pilot used his Curtiss JN-4 ‘Jenny’ in a single-handed raid on Haitian Cacos rebels. The JN-4 almost disintegrated in the pull-out, but the attack was effective, and the technique briefly tried further.
The rapid development of aircraft technology and its capability in the inter-war period is often under-estimated. While transports and airliners became inefficient as part-time bombers, airframe structural strength advances, enabled by stressed-skin construction and by more powerful engines, allowed aircraft to withstand greater forces.
The dive bomber was at the cutting edge of this: it needed to deal with a clearly quantified and necessary high-g pull-out, as well as managing speed in the preceding dive. This was either through straightforward strength in high drag airframes, or dive brakes – which themselves required appropriate structural support.
Meanwhile, fighter aircraft were expected to undertake high-speed straight line or curved ‘slashing’ attacks against bombers, and were not expected to engage in the high-g turning fights that were to develop into a reality in W.W.II.
Also, the doctrines of peacetime air force strategy should not be overlooked. Pre-war fighter theory focused on pure fighter-interceptors – ‘pursuits’ in the USAAF, hunters (‘Jaeger’) in Germany, or ‘interceptors’ in RAF fighter command. (Only the Royal Navy combined its fighter role with that of the dive bomber in the Blackburn Skua, but as a compromise solution.) Otherwise, it was simply not really conceivable or acceptable for fighter pilots to undertake a task like bombing.
The German plan
The Germans, forced to start with a clean slate, developed the idea further in the 1930s – accelerated (but not, despite the claims, initiated) by Ernst Udet’s use of Curtiss Hawk biplanes. The Germans settled on the Stuka* concept for a number of reasons, political ones among them, not least reflected in tussles within the Luftwaffe and directed by the views of Hitler himself.
There were several critical factors, however, in the late 1930s. An air force could get more single engine dive bombers for their money or war material than heavier conventional bombers. They were more accurate, particularly as the bomb sights available were not very good (most inter-war bomb sights were awful, and the accuracy of bombs dropped from height and tumbling wasn’t much better. Pointing the aircraft at the target and getting closer made sense.)
The Germans developed the concept of the Blitzkrieg, and this engendered the need to have small but critical targets taken out quickly and accurately for the fast-moving army. Dive bombers seemed to promise they could do that, and the artillery and conventional bombers were neither sufficiently accurate nor fast-reacting enough.
When, in May 1940, the British Expeditionary Force set up strong defensive positions on the west bank of the Oise River, Stukas broke the defence for the army, and the same happened to the French at Sedan. Dive bombers worked, and nothing else available would have done. This success was to cause the Germans to believe the Stuka could solve other problems which it could not.
One nut this approach did crack that hadn’t been part of the plan was a challenge the British, Japanese and Americans had been exploring themselves: sinking ships. The first success went to the British with the sinking of a major German warship. But to get to that, though, we need to go back to inter-war naval theory.
A naval need
The dive bomber offered the best compromise to naval strike aviation in the inter-war period. While Billy Mitchell was ‘proving’ that bombers could sink ships, the US Navy knew they could not carry bomber aircraft that large aboard their carriers, and that achieving penetration of armoured warships was tricky.
Ships were also a defined, often mobile and evasive target. In the same way that the German felt that the Stuka could hit an enemy defensive position but leave the area around it available for the German army to use in its advance, ships needed to be hit: near misses were not good enough.
Naval ships were also armoured, so the bombs used needed to be semi-armour piercing at least, and large enough to go through a ship’s horizontal or deck armour (often a weaker area in this era compared to the waterline and belt armour).
Navy success to Pacific divers
The German cruiser Koenigsberg was the first major warship ever sunk directly by dive bomber attack (or any kind of air attack) on 10 April 1940, and the first warship sunk by dive bombing by the Fleet Air Arm. This was the proof that the dive bomber could do the job as naval air power advocates had hoped.
The Royal Navy’s Blackburn Skua had been designed as a combined dive bomber and fighter, and while the Skua was just about an effective fighter against German bombers, it was unable to cope with dedicated enemy fighters.
After proving the dive bomber concept with the sinking of the Koenigsberg, the Royal Navy’s Skua squadrons suffered heavy losses during an attempt to bomb the German battlecruiser Scharnhorst at Trondheim on 13 June 1940: of fifteen aircraft in the raid, eight were shot down and the crews killed or taken prisoner, and the RN’s few later opportunities are often forgotten. It is ironic that the later Allied successes were with fighter-bombers, rather than with a bomber-fighters.
While at Pearl Harbor, nearly two years after the Koenigsberg’s sinking, Japanese Navy dive bombers were a major component of the attack, the effect of the still-developing capability of conventional bombers was demonstrated by the sinking of the Prince of Wales and Repulse by Japanese army conventional (and torpedo) bombers.
But the naval dive bomber achieved its greatest result when American Douglas SBD Dauntlesses scored fatal hits on three separate first-line Japanese aircraft carriers within six minutes at the Battle of Midway in June 1942, a decisive moment in the war’s history. Luck played its part, as did the sacrifice of VT-8’s TBD Devastator crews, but that does not detract from the SBD’s achievement. The US Navy’s adherence to the dive bomber had paid off. Afterwards, like other air forces, the Japanese and American navies hung onto the dive bomber too long, with the Curtiss SB2 Helldiver and the Yokosuka D4Y Suisei.
… And new weapons
After 1942, the dive bomber’s advantage was gone. Nearly as vulnerable as torpedo bombers, because they had to approach their target closely without major evasion, other methods being developed were simply better.
Near misses alluded to earlier were one of the things that changed in naval aviation. Bigger bombs could spring plates, rocket attacks and large calibre fixed guns were developed. New techniques were thought up: skip-bombing armour-piercing bombs into the side of a ship was a technique that required less skill, training and accuracy than dive bombing or using torpedoes.
Intriguingly, it was the Italian Ju 87 Stuka crews in their ‘Picchiatelli’ that developed the skip-bombing technique alongside their Luftwaffe colleagues in the Mediterranean.
This was in late 1940, after the Battle of Britain when many accounts state the Stuka were ‘a spent force’. The Stukas in the Med almost crippled the Royal Navy (the damage to HMS Illustrious being an example) and nearly turned that campaign in favour of the Axis (as in the Pedestal convoy action) – a dive bomber achievement that is often missed from the narrative.'
From the Stuka’s Med, to the Kittyhawk’s Africa
While the Stuka was achieving results in and around the Mediterranean, in North Africa the Commonwealth forces were exploring how effective hanging bombs on Curtiss Kittyhawks could be – and the Stuka was thus made obsolete in what was becoming a fighter-bomber’s war.
Fighter-bombers were no safer than dedicated dive bombers before they released their ordinance, but afterwards it was a whole different story. Considered from the point of view of cost, an aircraft able to undertake two roles was cheaper and logistically easier than two different dedicated types.
The other sign pointing to the future was also in the Mediterranean, when in 1943 the Italian battleship Roma was attacked by Luftwaffe Dornier Do 217 bombers with Fritz X stand-off radio controlled bombs. Just two of these, released from outside the range of the ship’s defensive fire, hit the ship, and it was sunk with 1,253 men. This attack was the first example of the modern anti-ship missile attack.
Not our idea: the RAF & the USAAF
In the mid-thirties, the RAF explored the dive-bomber idea with the Hawker Henley, but the idea was abandoned before the aircraft was even in service, and the Henley become a target tug. Promoted as a dive bomber in the pre-war press, the anti-dive bomber lobby in the RAF sidelined the role.
According to Flight, in 1937, “a high-ranking officer stated that dive-bombing was not practical in the R.A.F. because contemporary aeroplanes reached such high speeds in a dive that it would be very difficult to pull them out if, indeed, they did not break up in the air.”
Army support was also not a major RAF consideration, let alone integrated warfare like the Blitzkrieg. Perhaps it was a missed opportunity, but as air superiority had been lost in May 1940, it is unlikely they would have fared significantly better than the Fairey Battles.
The British then inherited the French orders for various aircraft, such as the heavily promoted Vought dive bomber, quickly relegated to second line use as the ‘Chesapeake’, and the Vultee Vengeance (which will be further examined in the next issue).
The pre-war USAAC liked the look of the ‘attack’ bomber rather than dive bombers, but in the mad scramble of the early war, dive bombers were acquired by accident, the Army versions of the Navy’s SBD being a disaster in use, partly due to the overwhelming Japanese strength at the time, as discussed previously by Michael Claringbold here.
Like the RAF, the USAAF also ended up with Vengeances they didn’t intend to use as dive bombers, and also quickly relegated.
German Stuka madness
The Germans’ initial trust and faith in the concept of the dive bomber grew into what can only be regarded as an unhealthy obsession with the type. Plans and successes of the early prototypes and the Ju 87 in Spain and in early W.W.II campaigns resulted in a childish desire for bigger, ‘better’ dive bombers.
The first notable example of this was the Junkers Ju 88, a superb aircraft in any context, but despite claims, not an effective dive bomber in reality.
The Ju 88 was able to undertake effective shallow dive bombing, achieving a very successful result, but the fundamental physics problem came into play and it was no real dive bomber. (It is worth mentioning at this point that ‘proper’ dive bombing involves a dive on the target of 60 – 90 degrees, not a 45 degree shallow dive, which is impressive and often effective enough for both delivery and recipient.)
Larger aircraft have more mass, and this is multiplied by acceleration – Newton’s physics all work against this enlargement with an exponential growth in problems for design and utilisation. Diving – and more critically – achieving a successful pull-out becomes a significantly larger challenge to structural strength.
Just to prove that how bad this course of growth was, the infamous requirement of the He 177 to be a dive bomber can only be regarded as ridiculous in concept and execution. The idea of using a medium bomber in proper pinpoint tactical dive bombing tasks was not efficient, the idea of such a huge mass and huge target of the He 177 hurtling towards a pinpoint objective cannot be entertained. In a way, the final victim of the myth of the Stuka was German planning.
When a Japanese target was attacked by Vultee Vengeance dive bombers, B-25 medium bombers and B-24 heavy bombers, the Vengeances achieved the greatest accuracy but the others obliterated it (and much of the surrounding area). The Allies’ use of fighter-bombers, medium and heavies was accurate enough while using greater volumes of bombs available. New weapons, such as rockets (and items like napalm), were easier, and often more effective. The Allies were happy with their sledgehammer on the nut.
Myth & counter myth
One problem the dive bomber acquired as a result of the European campaign of 1940 was that the dive bomber – the Stuka – was a tool of the enemy Blitzkrieg. There were no dive bombers that were ‘ours’. Part of the parcel of German warfare innovations, the Allies initially over-credited the Stukas and then, having faced the weapon and got its measure, swung to the opposite extreme and denigrated its importance.
The Axis’ success with the type is only reluctantly acknowledged today, despite the Stuka still being widely recognised in popular culture.
Today, only a few Stuka survive and only one is (relatively) complete and in dive bomber form. For one of W.W.II’s most important tools, it’s a very poor representation.
It is telling that, on the other hand, Pacific naval-air theory of both sides recognises the specific achievements and brief but telling successes of navy dive bombers in W.W.II combat, generally neither overstating nor denying their effect.
While the US Navy’s use of the SBD is appropriately and correctly recognised, the achievements of the Vengeance crews in the East and the early successes of the Royal Navy’s Skua crews have effectively been forgotten or written out of the narrative of W.W.II.
The dive bomber is often cited as being a failed concept because, first, dive bombers were not able to survive against enemy fighters, and second, they were not as useful as later fighters carrying bombs proved to be.
Neither is a fair judgement. The first task of any air force is to achieve and maintain air superiority. In W.W.II no tactical bomber force was able to survive against enemy fighters and carry out its task unless protected. (Fighter-bombers could defend themselves, but had to jettison bombs to do so if attacked on their way to target, and they would be in a disadvantageous position against the enemy’s fighters in those circumstances.)
In fact, dive bombers were no more vulnerable than any tactical level bomber. Was the dive bomber any use? The answer is clear.
The Luftwaffe’s Ju 87 Stukas were critical in the development and implementation of the Blitzkrieg, particularly in the mad days of the May 1940 advance. The unarguable critical Allied achievement was the US Navy’s SBD Dauntlesses at Midway. In both cases, they were a single weapon acting as part of a planned multi-disciplinary engagement, and were crucial in turning a campaign in timely strikes.
Dive bombers of the mind
No discussion of the effect of the dive bomber concept is complete without an examination of its psychological effects: positive and negative, frontline and cultural. Most discussions of the Junkers Ju 87 as the Stuka touch on the dive sirens – known to the Germans as the Jericho-Trompeten (‘Trumpets of Jericho’) – and their use as a weapon to throw off balance those on the receiving end of the Stuka’s attack.
It is important to note that the sirens were used both to misdirect those under attack, but also to distract practical opposition such as anti-aircraft gunners. This was essentially a defensive role for the siren, as well as the offensive role.
By the time the Trumpets of Jericho were being discussed in the Allied press, they had had their heyday and were being phased out due to their lack of surprise effect and because of drag. (Empty bottles thrown from aircraft had been used from the Great War forwards as a cheap psychological trick to imitate bombs. These were used in W.W.II by the RAAF Catalina crews on the long attacks on Japanese targets as an extra in a time of few real munitions.)
But we also forget that the Stuka had a positive effect in Germany. They were heavily promoted as a great German success in German cinemas and song (the literally bombastic films Stukas, Luftsieg über Polen and the song Stuka lied) gave the Germans on the home front and in combat a faith in the type that was already becoming less effective, and a faith that would cost them dear.
But the focus on the psychological effects of the dive bomber didn’t begin or end with
the German Blitzkrieg, nor was it always a negative effect on the adversaries.
The US Navy was probably the organisation that made the most of the perceived (rather than actual) value of the dive bomber. With aircraft picturesquely named ‘Hell Diver’ and with films featuring the aircraft (one itself called Hell Divers, released in 1931, apparently achieving impressive effects through superhuman flying skills) the idea of the dive bomber as something special was sold to the wider cinema-going public in the earliest stages of the dive bomber’s practical career.
While air speed record pilots gripped the public imagination of the 1950s, it was the ‘terminal velocity dive’ that had the cinema audience on the edge of their seats in the 1930s. No one bothered to notice that at that time, no ship had been sunk by a dive bomber.