The Franco-Belgian front holds 1940: consequences for the RAF?

Hi everyone,

I tend to be quite interested in discussing the details of a scenario where the Entente holds the front near the Franco-Belgian border in 1940 (mostly in other forums).

I was now wondering what the impacts would be for the RAF.

Obviously we may see fewer American aircrafts in service in the RAF owing to France keeping her orders and taking some of the American production capacity - unless continued French funding through the Anglo-French Purchasing Commission further accelerates the American industrial buildup.

In operational terms, there is obviously the huge difference of some of the RAF staying in France and thus operating closer to German targets, but with temporarily worse conditions than in the UK (less developped radar network), while the British Isles themselves may see far fewer German air attacks; and the AdA participating in the air war so that the RAF will never be alone for one year like it was IRL until the USSR and the US got involved.

But in terms of British procurement and technical development, would we see any significant changes from OTL?

While Franco-British synergies were a real thing in other areas, France doesn't appear to have anything to offer to the UK other than the swirl throttle technology (Szydlowski-Planiol supercharger), which the British already witnessed in later German aircrafts but didn't use; some Merlin cooling system test data (a French Merlin-equipped Amiot 356 bomber was meant to fly to Derby in May 1940 for study as its cooling system was allegedly showing interesting performance compared to Hurricane and Spitfire cooling systems); and somewhat faster 20mm HS-404 autocannon development.

Meanwhile, the reasoning for British air-industrial choices also don't really change and some decisions were already taken even before May 1940: the doomed Whirlwind/Peregrine program, the cancellation of many Rolls-Royce engine projects in favor of focusing on the Merlin, the airframe choices themselves.

Does somebody here have some insight about British decisions which were more directly influenced by the French defeat and may genuinely not have happened without it?

Elan Vital said:

While Franco-British synergies were a real thing in other areas, France doesn't appear to have anything to offer to the UK other than the swirl throttle technology (Szydlowski-Planiol supercharger), which the British already witnessed in later German aircrafts but didn't use; some Merlin cooling system test data (a French Merlin-equipped Amiot 356 bomber was meant to fly to Derby in May 1940 for study as its cooling system was allegedly showing interesting performance compared to Hurricane and Spitfire cooling systems); and somewhat faster 20mm HS-404 autocannon development.

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The S-P adjustable vanes were a good thing for improving the low-altitude power (same as with the swirl throttle by Polikovsky as installed on the Mikulin engines of ww2). If one has 2-speed S/C, appeal of the adjustable vanes is as good as lost, since the low-speed gearing takes care of the low-alt power. Doubly so if one has an basically unrestricted access to the high-octane fuel to further increase the boost as altitude is lower for greater power. Add the probably best S/C of 1940, as installed on the 2-speed supercharged Merlin XX, and there is not that much - if anything - that RR can learn.

Bristol might learn a thing or two from the S/C installed on the G&R 14R - still a 1-stage 2-speed device, but providing the altitude power no worse than BMW 801 despite the 14R being ~200 kg lighter engine.

The faster HS 404 development is certainly a boon; combined with no BoB as we know it might yield the much incresed might've.

Elan Vital said:

Meanwhile, the reasoning for British air-industrial choices also don't really change and some decisions were already taken even before May 1940: the doomed Whirlwind/Peregrine program, the cancellation of many Rolls-Royce engine projects in favor of focusing on the Merlin, the airframe choices themselves.

Does somebody here have some insight about British decisions which were more directly influenced by the French defeat and may genuinely not have happened without it?

Click to expand...

With France and Belgium holding out, British can press on with Spitfire III, thus negating much of problems that German fighters of 1941 brought. Peregrine was slated for cancellation due to the engine not being really mass-produced, so the price of engine was supposedly greater than that of the Merlin.

Defiant might get a bit longer life as a day fighter?

French defeat and the imminent invasion that never happened probably had a lot more importance on the tanks and anti-tank guns? A big change might be the lack of lend-lease law in the USA, but that is mostly taking effect in 1941.

Interesting premise, however I'd point out that by 1918 both sides had learned how to break into and through extensive trench defences. So holding the Germans at the Belgian border won't mean settling in for years, it will only be until the next offensive that even in failure could advance 100km.

That does mean France fights on though, so I could imagine the RAF becoming more of a tactical force, rather than the strategic force it became. Also without the bases on the French Atlantic coast the uboats won't be much of a strategic threat. I suspect more medium bombers and fighter bombers will be produced and there would be prolonged campaigns to gain even local air superiority. I think fighters would get longer range pretty quickly, because being to close to the front line would leave their bases vulnerable to land offensives.

tomo pauk said:

The S-P adjustable vanes were a good thing for improving the low-altitude power (same as with the swirl throttle by Polikovsky as installed on the Mikulin engines of ww2). If one has 2-speed S/C, appeal of the adjustable vanes is as good as lost, since the low-speed gearing takes care of the low-alt power. Doubly so if one has an basically unrestricted access to the high-octane fuel to further increase the boost as altitude is lower for greater power. Add the probably best S/C of 1940, as installed on the 2-speed supercharged Merlin XX, and there is not that much - if anything - that RR can learn.

With France and Belgium holding out, British can press on with Spitfire III, thus negating much of problems that German fighters of 1941 brought. Peregrine was slated for cancellation due to the engine not being really mass-produced, so the price of engine was supposedly greater than that of the Merlin.

Defiant might get a bit longer life as a day fighter?

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This is certainly true when comparing 2-speed Merlin XX or 61 to the single speed S39H3 S-P. My understanding is that a 2-speed swirl throttle would still improve performance a bit outside of the two rated altitudes, but I suppose the benefit would not really be worth the extra effort especially when production of the swirl throttle has not been prepared long in advance?

At the same time, if I go by the Secret Horsepower Race, integrating the two-speed Merlin into the Spitfire III still proved difficult even as of late 1940, so wouldn't the British still need the single-speed Merlin 45? In that case, the swirl throttle might be worth it. But given that coop on this regard still wasn't a thing as of mid-1940, maybe it was already too late to attempt a combined single-speed swirl throttle Merlin?

As for the other high alt French supercharging setups for inline engines (the 3-stage Farman/NC and the Hispano-Rateau or Hispano-Brown-Boveri turbochargers), they were probably only suitable for niche aircrafts.

Arguably, it might be perhaps easier to apply the swirl throttle supercharger to V-1710 rather than the Merlin? The French have more influence over the V-1710 owing to their large orders, and its supercharger itself is in greater need of upgrades than the Merlin.

Bristol might learn a thing or two from the S/C installed on the G&R 14R - still a 1-stage 2-speed device, but providing the altitude power no worse than BMW 801 despite the 14R being ~200 kg lighter engine.

Click to expand...

There is probably some value in studying the GR 14R's supercharger for Bristol, if its design was truly as good as it is believed. Too bad GR superchargers are extremely obscure.

The faster HS 404 development is certainly a boon; combined with no BoB as we know it might yield the much incresed might've.

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AFAIK the British wasted a lot of time working on a different belt feed than the French had been developping for the 20mm, so certainly beneficial. There are also claims of joint Anglo-French production of a 12.7 or 13.2mm Browning, so maybe France holding would keep this scheme alive.

I wonder if the Westland Whirwind would at least have had a more interesting operational life? The short range would be mitigated in France and it could be an especially useful boon in the air war over France and against any German bombing campaign of the French industry. The fighting altitude might be slighly more favourable than over Britain/the Channel as well.

French defeat and the imminent invasion that never happened probably had a lot more importance on the tanks and anti-tank guns? A big change might be the lack of lend-lease law in the USA, but that is mostly taking effect in 1941.

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Regarding ground weapons, true, the Franco-British synergies are both better known and more significant than in the air war.
The French were already delivering a decent number of 25mm AT guns to the BEF (among other weapons) and were set to deliver 100 47mm guns per month starting from late 1940, which would largely help the British. The British were also set to imminently deliver up to 80 H39 tank castings per month for the French industry, in exchange for some B1 Bis tanks starting from July, and a proportion of H39 later in 1940 to accelerate the expansion of the BEF.

Naturally, French supply of antitank guns relieves the British industry for further upgrades, while British supply of armor plate/castings was explicitly intended to free up French armor steel capacity for an even greater expansion of their battle tank production program (B1 and successors).

Rule of cool said:

Interesting premise, however I'd point out that by 1918 both sides had learned how to break into and through extensive trench defences. So holding the Germans at the Belgian border won't mean settling in for years, it will only be until the next offensive that even in failure could advance 100km. I think fighters would get longer range pretty quickly, because being to close to the front line would leave their bases vulnerable to land offensives.

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This is true, but the next offensive can only happen so soon after the previous one. As is even IRL Case Yellow and Red inflicted severe losses on the German mechanized branches (ground and air), while depleting the ammunition reserves needed for breakthroughs, which limits the 1940 campaign season to about July at the latest until the weather becomes unfavourable. For the next campaign season of Spring 1941, it is the Entente which is somewhat more favoured given the industrial situation.

So the front would not be stable for years...but not necessarily in a good way for the Germans.

That does mean France fights on though, so I could imagine the RAF becoming more of a tactical force, rather than the strategic force it became. Also without the bases on the French Atlantic coast the uboats won't be much of a strategic threat. I suspect more medium bombers and fighter bombers will be produced and there would be prolonged campaigns to gain even local air superiority.

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Didn't the British already intend to replace their medium bombers (Hampden, Whittley and others) with heavy ones in 1940? I don't recall any medium bomber successors in development even before May 40.
It's also worth noting that the British had launched a bombing campaign against German fuel industry and supplies in May 1940. With a better situation in France, it might actually grow into a larger and longer joint campaign while the stable front until Spring 1941 would not really promote a more tactical force, though the RAF would obviously have to be more balanced than IRL with a big ground front.

Elan Vital said:

Regarding ground weapons, true, the Franco-British synergies are both better known and more significant than in the air war.
The French were already delivering a decent number of 25mm AT guns to the BEF (among other weapons) and were set to deliver 100 47mm guns per month starting from late 1940, which would largely help the British.

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The 25mm ATG was inferior to the 2 Pdr, which was what British units should have had, but where they couldn't scale up production fast enough to ensure every BEF unit met its TOE, so France stepped in with the 25mm. Not sure which is superior wrt the 47mm APX and the 2 Pdr, but the French 75mm TAZ would definitely outperform both, especially with Brandt's DS round, and would become available if the line held. For the UK, not facing the losses of Dunkirk would mean the 6 Pdr could enter service on schedule, rather than being deferred for continued 2 Pdr production.

Didn't the British already intend to replace their medium bombers (Hampden, Whittley and others) with heavy ones in 1940? I don't recall any medium bomber successors in development even before May 40.

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There were at least five. The Manchester and HP.56 were originally intended as medium twins to P.13/36, but ended up as the Lancaster and HP.57 Halifax for various reasons. The Albemarle is effectively a medium bomber, though a compromised one by the decision to focus on non-strategic materials. The Warwick was a scaled up Wellington delayed by issues with the Vulture and Sabre, and the Blenheim replacement Beaumont ended up inflated into the Bristol Buckingham.

The example I would use is what the British did in the Med in 1941-43.

Fighting the real war, as opposed to planning with interwar theories tinged with the need to maintain budgets and independence through 2 lean decades, commanders in the Med didn't try to ramp up a strategic air campaign. With men, tanks and ships in contact with the enemy they had to do what worked, so focused on interdiction and attacks on base areas rather than trying to knock out Italian factories, oil refineries or other industrial targets.

In Britain, after the Blitz ended and Barbarossa started the RAF didn't have a lot of work to do so had the luxury to blunder blindly around Germany at night dropping bombs nowhere near their targets. However with an active front in France that luxury wouldn't exist, Bomber Command would have to support the Army like they did after Dunkirk by bombing German invasion barges and in 1944 by prepping northern France for invasion.

A blunted sickle (,pdf27 at ah.com)

Elan Vital said:

Hi everyone,

I tend to be quite interested in discussing the details of a scenario where the Entente holds the front near the Franco-Belgian border in 1940 (mostly in other forums).

I was now wondering what the impacts would be for the RAF.

Obviously we may see fewer American aircrafts in service in the RAF owing to France keeping her orders and taking some of the American production capacity - unless continued French funding through the Anglo-French Purchasing Commission further accelerates the American industrial buildup.

In operational terms, there is obviously the huge difference of some of the RAF staying in France and thus operating closer to German targets, but with temporarily worse conditions than in the UK (less developped radar network), while the British Isles themselves may see far fewer German air attacks; and the AdA participating in the air war so that the RAF will never be alone for one year like it was IRL until the USSR and the US got involved.

But in terms of British procurement and technical development, would we see any significant changes from OTL?

While Franco-British synergies were a real thing in other areas, France doesn't appear to have anything to offer to the UK other than the swirl throttle technology (Szydlowski-Planiol supercharger), which the British already witnessed in later German aircrafts but didn't use; some Merlin cooling system test data (a French Merlin-equipped Amiot 356 bomber was meant to fly to Derby in May 1940 for study as its cooling system was allegedly showing interesting performance compared to Hurricane and Spitfire cooling systems); and somewhat faster 20mm HS-404 autocannon development.

Meanwhile, the reasoning for British air-industrial choices also don't really change and some decisions were already taken even before May 1940: the doomed Whirlwind/Peregrine program, the cancellation of many Rolls-Royce engine projects in favor of focusing on the Merlin, the airframe choices themselves.

Does somebody here have some insight about British decisions which were more directly influenced by the French defeat and may genuinely not have happened without it?

Click to expand...

In my opinion the question is simple: the Allies expected a war of attrition based on enormous amounts of artillery, replacing the trenches with the Maginot Line. The plan was to hold out until the naval blockade forced the Germans to ask for an armistice. When the Panzers found themselves on the other end of the line and with the Luftwaffe achieving air superiority thanks to the new Bf 109 E, panic set in and politicians went into shock, blaming each other for cowardice. The deadly mistake was not to continue the construction of the Maginot Line to the sea, a political stupidity so as not to isolate Belgium.

Archibald said:

A blunted sickle (,pdf27 at ah.com)

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There's also La France Continue*, where France falls but the French fight on from North Africa. See here for links.

* And APOD, which forks off from the La France Continue timeline.

Elan Vital said:

At the same time, if I go by the Secret Horsepower Race, integrating the two-speed Merlin into the Spitfire III still proved difficult even as of late 1940, so wouldn't the British still need the single-speed Merlin 45?

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I have always wondered why Supermarine had so much trouble doing that and so little trouble integrating the Merlin 61 into an interim lash-up?

DWG said:

Not sure which is superior wrt the 47mm APX and the 2 Pdr, but the French 75mm TAZ would definitely outperform both, especially with Brandt's DS round, and would become available if the line held. For the UK, not facing the losses of Dunkirk would mean the 6 Pdr could enter service on schedule, rather than being deferred for continued 2 Pdr production.

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The 75mm TAZ was however not suitable as a common light/medium antitank gun like the 2/6pdr and 47mm. The French were rather explicit in the fact that their production capacity for medium calibre guns (75 and up) was limited, with the 75mm TAZ also being a heavy asset which would fit a different role, more like the 17 pdr. So for the UK, the step-up from the 2pdr will remain the 6pdr when it becomes available, and the 47mm in the interim/as a supplement until 6pdr production picks up enough.

There were at least five. The Manchester and HP.56 were originally intended as medium twins to P.13/36, but ended up as the Lancaster and HP.57 Halifax for various reasons. The Albemarle is effectively a medium bomber, though a compromised one by the decision to focus on non-strategic materials. The Warwick was a scaled up Wellington delayed by issues with the Vulture and Sabre, and the Blenheim replacement Beaumont ended up inflated into the Bristol Buckingham.

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Interesting. In practice for this scenario, the HP 56 had already morphed into the HP 57 before 1940 and the odds of the Vulture being supported remain low. The Albemarle was apparently not performing well-enough to remain as a bomber, leaving the Warwick which was facing shortages of engines (and with France still there to go after the R-2800s the Warwick got, competition for the engine will be even more severe!); and the Buckingham which was apparently very late.

So it seems that the industrial situation by mid 1940 already condemned British medium bombers until 1943 at best, unless they reprioritize engines for them.

The French were in the opposite situation, not being able to expect domestic heavy bombers until late 1941 at the earliest, but working towards a medium bomber fleet.

I have always wondered why Supermarine had so much trouble doing that and so little trouble integrating the Merlin 61 into an interim lash-up?

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@pathology_doc Ditto, the Spit IX ended up fitting it with a longer nose (and obviously some counterweight was needed). One can only assume that the British were so desperate to limit production line changes that they preferred keeping the short nose for the Spit V, requiring the Merlin 45. But if you need some change for the engine line to produce the new supercharger, wouldn't there be excess airframe production that you can afford to cut anyway?

Elan Vital said:

This is certainly true when comparing 2-speed Merlin XX or 61 to the single speed S39H3 S-P. My understanding is that a 2-speed swirl throttle would still improve performance a bit outside of the two rated altitudes, but I suppose the benefit would not really be worth the extra effort especially when production of the swirl throttle has not been prepared long in advance?

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S/C on the Merlin 61 was not only with 2-speed gear, but it was also of the 2-stage version, that greatly improved power above 20000 ft.

Elan Vital said:

At the same time, if I go by the Secret Horsepower Race, integrating the two-speed Merlin into the Spitfire III still proved difficult even as of late 1940, so wouldn't the British still need the single-speed Merlin 45? In that case, the swirl throttle might be worth it. But given that coop on this regard still wasn't a thing as of mid-1940, maybe it was already too late to attempt a combined single-speed swirl throttle Merlin?

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Integration of the 2-speed Merlin (the Mk.XX) went as good as possible on the Spitfire III; later (1942) one of the prototypes even received the 2-stage Merlin 61. Problem was that the Mk.XX was required for the Hurricane II in order to cancel out the performance advantage possessed by the Bf 109E, so Spitfires gotten the Merlin XII (as well as the improved protection) becoming Spitfire II.
Yes, the swirl throttle would've been good for the 1-speed Merlin 45, that lacked the low gear for it's S/C. Note that both Merlin 45 and XX were outfitted with much better superchargers than it was the case with Merlin III or the XII.

It was probably too bad that Spitfire III was not outfitted with Merlin XII, in order to take advantage of it's aerodynamic improvements (internal BP glass, fully covered wheel wells, retractable tailwheel) - perhaps resulting in a 370+ mph fighter for BoB? Increased fuel tankage would've also come in handy.
Later (1941) move to Merlin 45, for another 15+- mph?

Elan Vital said:

Arguably, it might be perhaps easier to apply the swirl throttle supercharger to V-1710 rather than the Merlin? The French have more influence over the V-1710 owing to their large orders, and its supercharger itself is in greater need of upgrades than the Merlin.

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Supercharger of the V-1710 (without talking about the turbo versions) needed improvements for it's power at higher altitudes, that was lacking due to the too small impeller rotating at modest speeds. Swirl throttle can bring the improvement at lower altitudes, but not at higher altitudes.

Elan Vital said:

There is probably some value in studying the GR 14R's supercharger for Bristol, if its design was truly as good as it is believed. Too bad GR superchargers are extremely obscure.

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This is the only data from a primary source that I'm aware of the 14R: link
Making 1320 PS at almost 6 km, and that is the 30 min rating (ie. still not the best available power setting) was better value than what the fully-rated BMW 801D did in late 1942 and on. Bristol Hercules engines managed to beat this by late 1944, after the full redesign of the S/C - so certainly there is something to learn here.

Elan Vital said:

Naturally, French supply of antitank guns relieves the British industry for further upgrades, while British supply of armor plate/castings was explicitly intended to free up French armor steel capacity for an even greater expansion of their battle tank production program (B1 and successors).

Click to expand...

Without the invasion scare, the 6pdr would probably see the combat as early as late 1940, and certainly by early 1941.

Elan Vital said:

Didn't the British already intend to replace their medium bombers (Hampden, Whittley and others) with heavy ones in 1940? I don't recall any medium bomber successors in development even before May 40.

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British regarded the Whitley and Wellington (and maybe Hampden) as heavy bombers, while the Blenheim (and Battle, and later Mosquito) were called the light bombers; yes, indeed, RAF was moving onto 4-engined bombers already by 1940, with some 2-engined designs also in pipeline.
As noted above, serious problems with 2000+ HP British engines relegated these 2-engined bombers into non-starters for the intended role.

Rule of cool said:

Fighting the real war, as opposed to planning with interwar theories tinged with the need to maintain budgets and independence through 2 lean decades, commanders in the Med didn't try to ramp up a strategic air campaign.

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Not having a sizable force of heavy bombers, and not having enemy industry in range for day-after-day bombing kinda puts the stops on the attempt for a strategic air campaign

pathology_doc said:

I have always wondered why Supermarine had so much trouble doing that and so little trouble integrating the Merlin 61 into an interim lash-up?

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There was no trouble in installing the Mk.XX on the Spitfire III.
Trouble was the lack of Mk.XXs both for Spitfire and Hurricane, the later needing it much more than the former.

On the ground side, the change to the 6pd as originally planned would greatly help the British tanks. Would probably push the Germans to uparmor sooner as well.

Crud, just not losing all that war materiel at Dunkirk would be a huge help to the UK.

And not having the French ports to sally from would greatly reduce the U-boat threat, which makes getting US lend-lease a lot easier.

But back to the ground. I suspect better ability to destroy German tanks would make the Africa campaign shorter, since it'd force Rommel to have fewer tanks available for his pushes.

Likewise, the Soviets getting Valentine tanks with 6pdrs instead of 2pds would possibly shorten the war on their side.

Scott Kenny said:

On the ground side, the change to the 6pd as originally planned would greatly help the British tanks. Would probably push the Germans to uparmor sooner as well.

Crud, just not losing all that war materiel at Dunkirk would be a huge help to the UK.

And not having the French ports to sally from would greatly reduce the U-boat threat, which makes getting US lend-lease a lot easier.

But back to the ground. I suspect better ability to destroy German tanks would make the Africa campaign shorter, since it'd force Rommel to have fewer tanks available for his pushes.

Likewise, the Soviets getting Valentine tanks with 6pdrs instead of 2pds would possibly shorten the war on their side.

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No such thing as an African campaign or Eastern front with mainland France in the fight. I have seen inconclusive info on the willingness of the Italians to exploit the distraction of the Entente by the Germans, but even then that front is as good as dead with French colonial forces and the Navy operational to assist the British. Sparing Rommel will be near impossible as well with a busy Franco-Belgian front.

Attacking the Soviets while the Entente is going strong is a similar deal.

Elan Vital said:

Attacking the Soviets while the Entente is going strong is a similar deal.

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Germany might yet be forced into that as a pre-emptive necessity in case Stalin figures that this is the time to stab his erstwhile ally in the back. The difference is that there won't be any full-on drive to Moscow; it will be a case of inflicting the maximum possible amount of attrition on the Soviets in the opening week or so and then going over to a defensive posture with the entirety of Poland as a buffer.

In the absence of the massive expenditure of men and arms that Germany undertook pushing no further than the outskirts of Moscow (even Napoleon actually managed to take it, for all the good that did him) and the absence of distracting sideshows, the war takes a different flavour. Note that one of the things Germany wanted in French North Africa (and which it lost when kicked out from there) is supplies of cobalt etc. for engine steels. Not having those is going to make its aero engines start becoming worse sooner.

Elan Vital said:

No such thing as an African campaign or Eastern front with mainland France in the fight.

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That's dependent on whether Mussolini has the sense to sit things out or not. If he doesn't then Libya, Ethiopia and Italian East Africa need dealing with.

pathology_doc said:

Germany might yet be forced into that as a pre-emptive necessity in case Stalin figures that this is the time to stab his erstwhile ally in the back. The difference is that there won't be any full-on drive to Moscow; it will be a case of inflicting the maximum possible amount of attrition on the Soviets in the opening week or so and then going over to a defensive posture with the entirety of Poland as a buffer.

In the absence of the massive expenditure of men and arms that Germany undertook pushing no further than the outskirts of Moscow (even Napoleon actually managed to take it, for all the good that did him) and the absence of distracting sideshows, the war takes a different flavour. Note that one of the things Germany wanted in French North Africa (and which it lost when kicked out from there) is supplies of cobalt etc. for engine steels. Not having those is going to make its aero engines start becoming worse sooner.

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The war would indeed be very different. Historical WW2 in Europe expanded very quickly to the entire Continent and was largely fought in degraded logistical conditions (Western USSR, bombed-out 1944-45 Western Europe, North Africa, multiple sea landings needed).
Here, most forces would be concentrated on the fairly narrow Franco-Belgian and Franco-German borders at least until the Germans or the Entente can go on the offensive again over the Benelux; while the supply lines would be very well established behind the front of both factions (French railway network operational).
It's not so simple for Germany to devote personnel to operations elsewhere: the French forces as they were represented 4-5 million mobilized personnel with the British still having plenty of slack to ramp up, and with a now potent industry to back them up. Germany in late 1940 would already be in the situation they were in in late 1941/42 against the USSR, but without that extra year to train new recruits, next to no captured Entente equipment and with their enemy not having had to relocate their entire industry and not having lost a huge portion of the pre-invasion forces. So it would be difficult for Germany to launch a preemptive offensive against the USSR.

That said, neither side in 1940 and possibly 1941 for that matter had many troops to spare to expand to new fronts. The French kept an eye on the neutral/Entente-friendly central European and Balkan countries, and was already sending them some aid and preparing an expeditionary force so that they could resist a German invasion, but it would take a lot more help before these countries themselves entered the war on the Entente's side. A lot would probably depend on Italy's opportunism.

Yes, I remember the French North African cobalt from The Secret Horsepower race, that and French ressources being out of Germany's reach will put a severe limitation on the ability of the Germans to ramp up their military production.

DWG said:

That's dependent on whether Mussolini has the sense to sit things out or not. If he doesn't then Libya, Ethiopia and Italian East Africa need dealing with.

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True, from what little I have seen on the subject, jury's still out on whether the fascist regime was going to be opportunistic even with France still in the fight but distracted. At the very least this was a possibility the French seriously considered, hence their efforts to prepare the Balkans and an expeditionary force in the Levant which could be deployed either in North Africa or the Balkans in case of German or Italian invasion.
While the losses on the Northeastern front (the French name for the Franco-Belgian theater) during the 1940 offensives would probably require some extra reinforcements from North Africa and delayed material reinforcement of the latter, it would still be a complicated prospect for Italy with the French Navy and colonial forces being available and even the Royal Navy might have more to spare with the Kriegsmarine being better contained without French ports.

Elan Vital said:

from what little I have seen on the subject, jury's still out on whether the fascist regime was going to be opportunistic even with France still in the fight but distracted. At the very least this was a possibility the French seriously considered, hence their efforts to prepare the Balkans and an expeditionary force in the Levant which could be deployed either in North Africa or the Balkans in case of German or Italian invasion.

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That's a good point about possible Italian adventurism in the Balkans, which has the potential to draw them into the war even without an intentional declaration of war vs France.

Elan Vital said:

Hi everyone,

I tend to be quite interested in discussing the details of a scenario where the Entente holds the front near the Franco-Belgian border in 1940 (mostly in other forums).

I was now wondering what the impacts would be for the RAF.

Obviously we may see fewer American aircrafts in service in the RAF owing to France keeping her orders and taking some of the American production capacity - unless continued French funding through the Anglo-French Purchasing Commission further accelerates the American industrial buildup.

In operational terms, there is obviously the huge difference of some of the RAF staying in France and thus operating closer to German targets, but with temporarily worse conditions than in the UK (less developped radar network), while the British Isles themselves may see far fewer German air attacks; and the AdA participating in the air war so that the RAF will never be alone for one year like it was IRL until the USSR and the US got involved.

But in terms of British procurement and technical development, would we see any significant changes from OTL?

While Franco-British synergies were a real thing in other areas, France doesn't appear to have anything to offer to the UK other than the swirl throttle technology (Szydlowski-Planiol supercharger), which the British already witnessed in later German aircrafts but didn't use; some Merlin cooling system test data (a French Merlin-equipped Amiot 356 bomber was meant to fly to Derby in May 1940 for study as its cooling system was allegedly showing interesting performance compared to Hurricane and Spitfire cooling systems); and somewhat faster 20mm HS-404 autocannon development.

Meanwhile, the reasoning for British air-industrial choices also don't really change and some decisions were already taken even before May 1940: the doomed Whirlwind/Peregrine program, the cancellation of many Rolls-Royce engine projects in favor of focusing on the Merlin, the airframe choices themselves.

Does somebody here have some insight about British decisions which were more directly influenced by the French defeat and may genuinely not have happened without it?

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This is what the French Army trained and was equipped for, a modern version of the Western Front of World War I.

DWG said:

That's dependent on whether Mussolini has the sense to sit things out or not. If he doesn't then Libya, Ethiopia and Italian East Africa need dealing with.

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And considering that Mussolini was already active there before the war started, then the Afrika Korps still happens.

One consequence might be greater demands from the Army for its own air support.
In early 1940 the trial AOP unit D Flight arrived in France but was still very much in the early phases and still testing suitable aircraft, including autogiros loaned by the French for tests. Three Stinsons and a Taylorcraft Model D arrived just before the German invasion. The RAF ordered the unit to disband but its CO managed to stave that off with Army support.
Earlier in October 1939 the Army had asked for 250 ground attack aircraft - which the RAF rebuffed, giving them support for the AOP concept (including training and ground support) as this was cheaper for them than giving up bombers.

The first AOP unit, 651 Sqn did not form until August 1941. It's possible that in this scenario that such units would form by the winter of 1940 - quite what they would fly in open to question, probably Taylorcraft and other light 'odds and sods' in the absence of anything better (Stinson Vigilants wouldn't arrive until 1942 and were soon found to be too large).

But it might also open up the possibility of a call for ground support aircraft if Army Co-operation Command failed to give enough support. It's likely that that command would have to introduce fighters as fighter-bombers by 1941 in order to remain credible, Lysanders wouldn't cut it and transferring Battles would be no better. I doubt that the Hawker Henley decision could be reversed, by 1940 the production as target tugs was well underway, though its possible some of Gloster's Hurricane orders might have been converted to dive-bomber Henleys for delivery from 1941 onwards.

Scott Kenny said:

And considering that Mussolini was already active there before the war started, then the Afrika Korps still happens.

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I can't help thinking Yugoslavia will be an unbearable temptation for him, and then that inevitably goes wrong and draws Germany in. The difference will be the impact of the French forces in the Levant being on the spot to reinforce Yugoslavia and Greece.

France had massive military forces in North Africa. OTL, all alone the british almost wiped out the italians of North Africa late January 1941 - the A.K saved Mussolini sorry ass at the last hour. In fact the Stukas bombing the crap of Illustrious essentially turned the tide.
-If France military forces in N.A join the British, the italians are toast long before the A.K come saving their asses. In France Fights On, even with the metropole lost, broken back and exiled to Algiers, it's over by October 1940.
If the metropole survives in May, it should be even shorter.

Hood said:

I doubt that the Hawker Henley decision could be reversed, by 1940 the production as target tugs was well underway, though its possible some of Gloster's Hurricane orders might have been converted to dive-bomber Henleys for delivery from 1941 onwards.

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Considering that the Hurricane made the transition to ground attack aircraft and tank buster anyway, I think it's pretty obvious how the fighter-bomber evolves once the Hurricane is no longer competitive in the air-superiority role. Even if it's not a frontline interceptor any more, it can still put up a good fight in its own defence.

The other aircraft I'd consider for army support is the Skua, since it's already in production for the FAA with logistical support in place, and it means you don't have to waste time getting dive-bomber Henley production set up. Sure, it might be no more than a gap-filler until something better comes along, but it's there.

Greg Baughen's book about the Battle argues that the aircraft was badly used and had untapped potential, but comes across as somewhat hagiographic. Nevertheless, one might ask what can be done with a Battle that was better engined (e.g. Merlin 32 or low-blown 40-series), armed and armoured.

I still think an uprated Skua is a better bet as an interim ground support aircraft, though, because it requires far less development time.

pathology_doc said:

Considering that the Hurricane made the transition to ground attack aircraft and tank buster anyway, I think it's pretty obvious how the fighter-bomber evolves once the Hurricane is no longer competitive in the air-superiority role. Even if it's not a frontline interceptor any more, it can still put up a good fight in its own defence.

The other aircraft I'd consider for army support is the Skua, since it's already in production for the FAA with logistical support in place, and it means you don't have to waste time getting dive-bomber Henley production set up. Sure, it might be no more than a gap-filler until something better comes along, but it's there.

Greg Baughen's book about the Battle argues that the aircraft was badly used and had untapped potential, but comes across as somewhat hagiographic. Nevertheless, one might ask what can be done with a Battle that was better engined (e.g. Merlin 32 or low-blown 40-series), armed and armoured.

I still think an uprated Skua is a better bet as an interim ground support aircraft, though, because it requires far less development time.

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Sounds like a close match to French progression from the LN 401 towards the LN 42 dive bomber.

The tactical ground attack element of the RAF might converge towards something very similar to what the French were working towards in the end (Skua/Battle & Beaufighter on the British side and LN 42/Breguet 693/95 on the French side).

pathology_doc said:

The other aircraft I'd consider for army support is the Skua, since it's already in production for the FAA with logistical support in place, and it means you don't have to waste time getting dive-bomber Henley production set up. Sure, it might be no more than a gap-filler until something better comes along, but it's there.

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Not a terrible idea. But it would only be a gap filler given that the Perseus lacks upgrade potential and the airframe is too small for a twin-row radial.
The Fairey dive-bomber that became the Fulmar could be interesting too.

When was Specification B.20/40 issued, before or after the Battle of France? I'd assume any British Close Support Aircraft/Dive Bomber would meet that something like that requirement, in which case we would be looking at the Boulton Paul P.95, Fairey's de-navalised Barracuda or the Hawker P.1006 development of the Henley.

Hood said:

But it would only be a gap filler given that the Perseus lacks upgrade potential and the airframe is too small for a twin-row radial.

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About the only thing you could do to it is maybe increase the boost a little with 100 octane fuel and put a constant-speed prop on it.
I did see this...

The result was a Bristol Mercury-sized engine adapted to the sleeve valve system, the Perseus, and its smaller cousin, the Bristol Aquila. The first production versions of the Perseus were rated at 580 horsepower (433 kW), the same as the Mercury model for that year, which shows that the sleeve system was being underexploited. The engine was quickly uprated as improvements were introduced and by 1936 the Perseus was delivering 810 hp (604 kW), eventually topping out at 930 hp (690 kW) in 1939, while the Perseus 100 with an increased capacity of 1,635 cu in (26.8 L), produced 1,200 hp (890 kW) at 2,700 rpm at 4,250 ft (1,296 m).[3] This far outperformed even the most developed versions of the Mercury.

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...and if this "Perseus 100" is both early enough and still small enough to fit in the Skua, there is potential for significant performance improvement. But mostly, yes, I'm suggesting it as a gap filler.

Hood said:

Not a terrible idea. But it would only be a gap filler given that the Perseus lacks upgrade potential and the airframe is too small for a twin-row radial.
The Fairey dive-bomber that became the Fulmar could be interesting too.

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I've long thought P.4/34 was a missed opportunity, and you don't need to roll back the Fulmar design to the earlier design so much as accelerate the Fulmar Mk II provisions for centre-fuselage drop tank/250lb/500lb. And of course it's an aircraft entering production, rather than already out of it as the Skua was. (And ISTR Fulmars did night intruder work out of Malta - mentioned here: https://maltagc70.wordpress.com/tag/fairey-fulmar/).

The other alternative for the Henley would be to divert some of the Canadian CC&F Hurricane production to Henley.

A Tentative Fleet Plan said:

When was Specification B.20/40 issued, before or after the Battle of France? I'd assume any British Close Support Aircraft/Dive Bomber would meet that something like that requirement, in which case we would be looking at the Boulton Paul P.95, Fairey's de-navalised Barracuda or the Hawker P.1006 development of the Henley.

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According to BSP 4, the responses were either 11.40, or 'Late 40', which suggests it was probably issued sometime during the summer or early autumn, and likely after the Battle of France. The British Aircraft Specification List doesn't have a date for B.20/40, but gives the following for other specifications: 15/49 27-7-40, F.16/40 4-11-40, 17/40 31-10-40, F.18/40 10-11-40, F.19/40 9-9-40.

pathology_doc said:

Considering that the Hurricane made the transition to ground attack aircraft and tank buster anyway, I think it's pretty obvious how the fighter-bomber evolves once the Hurricane is no longer competitive in the air-superiority role. Even if it's not a frontline interceptor any more, it can still put up a good fight in its own defence.

The other aircraft I'd consider for army support is the Skua, since it's already in production for the FAA with logistical support in place, and it means you don't have to waste time getting dive-bomber Henley production set up. Sure, it might be no more than a gap-filler until something better comes along, but it's there.

Greg Baughen's book about the Battle argues that the aircraft was badly used and had untapped potential, but comes across as somewhat hagiographic. Nevertheless, one might ask what can be done with a Battle that was better engined (e.g. Merlin 32 or low-blown 40-series), armed and armoured.

I still think an uprated Skua is a better bet as an interim ground support aircraft, though, because it requires far less development time.

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Skua production had ended at the Blackburn Brough site at the end of 1939 beginning of 1940 with the Air Ministry having told Blackburn that there would be no further orders for it as far back as March 1939. That allowed Blackburn to concentrate on the Botha contract.

While the Roc was designed by Blackburn, production was sub-contracted to Boulton Paul (contract July 1937) to allow Blackburn to concentrate on Skua & Both a.

From mid-1939 the design dept was working on what became the Firebrand, intended as the next navy fighter.

The Dumbarton factory moved from Botha to Sunderland (1939 contract, first delivery Nov 1941)

The Blackburn Sherburn-in-Elmet factory had been planned from the outset for Admiralty production. Initially Albacore but switched to Swordfish as it used less in the way of strategic materials and could use Fairey jigs and expertise to get up and running which didn't work out as planned. First "Blackfish" came off the line in Oct 1940 (Fairey production ceased in Feb 1940 as Albacore production started at Hayes)

pathology_doc said:

The other aircraft I'd consider for army support is the Skua, since it's already in production for the FAA with logistical support in place, and it means you don't have to waste time getting dive-bomber Henley production set up. Sure, it might be no more than a gap-filler until something better comes along, but it's there.

Greg Baughen's book about the Battle argues that the aircraft was badly used and had untapped potential, but comes across as somewhat hagiographic. Nevertheless, one might ask what can be done with a Battle that was better engined (e.g. Merlin 32 or low-blown 40-series), armed and armoured.

I still think an uprated Skua is a better bet as an interim ground support aircraft, though, because it requires far less development time.

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I'd also second the Skua suggestion.
It was a smaller aircraft than the Battle (= will be harder to hit), and can be easily up-engined with the Pegasus engine, so the altitude performance is much improved vs. the Perseus-powered historical type, and it does not draw on the Merlins' supply. Frontal firepower is much better with 4 .303s.

Battle was certainly badly used, however Germans managed to loose Ju-87s in scores against RAF even with LW providing the fighter escort - my point is that Battle will be always a rewarding target both for the Flak and fighters. Installing more HP and providing actual protection will still mean a sizable ( size of Bf 110) & slow bomber - to the joy of AA gunners and experten alike. We can recall than Germans have had in service more than 10000 (ten thousand) light Flak guns already in 1940, as well as more than 3000 of heavy pieces - a bomber/attacker being small, fast, resilient and maneuverable is a recipe for making it above Western Europe in 1940 and on.

Battle, in combat role, might've found the second lease of life as a torpedo/patrol bomber to cover areas away from the enemy fighters, and it might do less worse with major engine, protection and firepower upgrade against the Japanese in 1941/42.

Hood said:

The Fairey dive-bomber that became the Fulmar could be interesting too.

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Either that, or the mass-produced Henley in it's intended role would've make for a good what-if story... Both aircraft were supposed to be faster than Battle by 40 mph, on same engine.
Perhaps even a night-fighter spin off?

pathology_doc said:

I did see this... "The engine was quickly uprated as improvements were introduced and by 1936 the Perseus was delivering 810 hp (604 kW), eventually topping out at 930 hp (690 kW) in 1939, while the Perseus 100 with an increased capacity of 1,635 cu in (26.8 L), produced 1,200 hp (890 kW) at 2,700 rpm at 4,250 ft (1,296 m).[3] This far outperformed even the most developed versions of the Mercury."
...and if this "Perseus 100" is both early enough and still small enough to fit in the Skua, there is potential for significant performance improvement. But mostly, yes, I'm suggesting it as a gap filler.

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Talk about misleading stuff we can find at Wikipedia

Perseus 100 was basically one half of the Centaurus, and was a post-war thing (that was never flown in service?). Development of the Mercury stopped in 1940? Increased capacity matters, development in engine strength matters, greater fining of the radials matters, improvement of S/C (hopefully it was done? the pre-1943 S/Cs at Bristol were awful) also matters, better fuel matters... But apparently not for the article's writer.

We can recall that already the German 9-cyl ww2 radials, when using high octane fuel, were already making 1100-1200 HP. With just the humble two poppet valves per cylinder.
The R-1820 was making 1300 HP+ already in late 1943, as an actual engine made in thousands. Post-war versions made more than 1400 HP.

Skua production had ended at the Blackburn Brough site at the end of 1939 beginning of 1940 with the Air Ministry having told Blackburn that there would be no further orders for it as far back as March 1939. That allowed Blackburn to concentrate on the Botha contract.

While the Roc was designed by Blackburn, production was sub-contracted to Boulton Paul (contract July 1937) to allow Blackburn to concentrate on Skua & Both a.

From mid-1939 the design dept was working on what became the Firebrand, intended as the next navy fighter.

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Talk about an unfortunate string of pathetic failures. Reverse King Midas ! Whatever Blackburn designed surely did not turned into gold. Led maybe ? (and I'm charitable here, me thinks)

tomo pauk said:

Talk about misleading stuff we can find at Wikipedia

Perseus 100 was basically one half of the Centaurus, and was a post-war thing (that was never flown in service?).

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Ah well, so much for that idea, then.

EwenS said:

Skua production had ended at the Blackburn Brough site at the end of 1939

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Was there no replacement of losses, then? Or did the numbers of squadrons in service allow adequate replenishment from existing post-production stocks?

Archibald said:

Talk about an unfortunate string of pathetic failures. Reverse King Midas ! Whatever Blackburn designed surely did not turned into gold.

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They did, at the end, redeem themselves with the Buccaneer. Saving the best for last, it seems. But so many Blackburn aircraft could easily fall under the unflattering category of "fugly".

pathology_doc said:

Was there no replacement of losses, then? Or did the numbers of squadrons in service allow adequate replenishment from existing post-production stocks?

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If you stop and think about it the pre-war FAA didn't need hundreds of Skuas and the associated reserves. By 1938 the main carriers were Courageous, Glorious, Furious (requiring 1 fighter squadron each with 12 aircraft) plus Ark Royal (2 squadrons with 9 each) for a front line strength of 54. Production run was planned as 190 with the "interim" replacement being the Fulmar expected in service by the end of 1939. The Illustrious class were expected in service from early 1940.

(Argus was converted to an auxiliary Queen Bee carrier 1936-38 to free up Treaty tonnage for Ark Royal. Eagle & Hermes were too small for fleet use. In 1939 and looking forward to 1942 Hermes was noted as a trade protection carrier while Eagle was missing altogether.)

So in the end only 4 front line squadrons used the Skua - 800, 801, 803 & 806.

Only 5 front line squadrons used the Roc - 800, 801, 803, 805 & 806.

Of those, 806 only used them between formation in Feb 1940 until July 1940 when it converted to Fulmars and deployed on Illustrious to the Med.

805 was intended to operate Roc floatplane fighters. As that didn't proceed beyond the sole prototype, the squadron existed for only 9 days in May 1940.

800 used Skuas until April 1941 and 803 until Oct 1940 moving on to Fulmars at that point plus 801 until May 1941. The Roc had an even shorter life.

Edit. The 136 Rocs also need figured into the equation.

pathology_doc said:

... I still think an uprated Skua is a better bet as an interim ground support aircraft, though, because it requires far less development time.

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If Battle production is being scaled back, dare I suggest a Merlin-powered Skua derivative?
-- https://www.secretprojects.co.uk/threads/apophenias-art.43227/#post-716105

The linked-to image is an old what-if for Beyond the Sprues. It is of a naval variant but gives the idea of a re-engined Skua.

Something I've been thinking about: did the British aero industry lose some supplies of manufactured parts or raw materials from France when it was lost?
I know from French documents that there was a big effort to increase economic cooperation between the two countries to cover gaps in each other's production, but in terms of raw materials or finished parts this was usually in favor of the French, so I wonder if the British were procuring parts or materials from France.
In that case, not losing metropolitan France could avoid or mitigate certain shortages, without even considering the benefits regarding supplies going accross the Atlantic to the UK from a Battle of the Atlantic that is more favourable to the Entente.

Elan Vital said:

Something I've been thinking about: did the British aero industry lose some supplies of manufactured parts or raw materials from France when it was lost?
I know from French documents that there was a big effort to increase economic cooperation between the two countries to cover gaps in each other's production, but in terms of raw materials or finished parts this was usually in favor of the French, so I wonder if the British were procuring parts or materials from France.
In that case, not losing metropolitan France could avoid or mitigate certain shortages, without even considering the benefits regarding supplies going accross the Atlantic to the UK from a Battle of the Atlantic that is more favourable to the Entente.

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Materials I'd expect, like aluminum.

Scott Kenny said:

Materials I'd expect, like aluminum.

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Gold, Uranium, pilots, patents