The most secret weapon of the Luftwaffe

[Milosh]

Actually, the Ta183 was built postwar as the Brazilian Pulqui II and one of the 4 even saw combat.

If you look at the Ta183 concepts, the most popular design was V1 that people associate with the Ta183. However, after extensive testing and modifications, it was V3 that was decided to produce, but time ran out before anything came of it.

The Russians did get the plans, and it's been said they built and flew it...and apparently, they borrowed several design features although Russian historian Yefim Gordon says that the MiG-15 was completely a native design with no western influence...

This is the Brazilian "Ta183" AKA the Pulqui:

View attachment 305368

Hmmm...sure looks familiar, doesn't it?

That should be Argentina not Brazil. It had its own flight problems.

 

[tyrodtom]

Kurt Tank was head of the Pulgui IIs design team. 4 prototypes built, 2 crashed with fatalities.
The only combat one prototype was in being the Coup De'tat against Peron in 1955.

One of the Horton brothers went to work for a aircraft concern in Brazil after WW2. Built several fairly successful glider flying wings, and one unsuccessful cargo flying wing.
I can see no proof that either of the Horton brothers could get anyone interested in continuing development of their WW2 military designs.

 

[GrauGeist]

I thought the Pulqui was Argentinian

That should be Argentina not Brazil. It had its own flight problems.

Yep...Argentina!

I have no idea why Brazil got in there and I can't even blame it as a typo

...I can see no proof that either of the Horton brothers could get anyone interested in continuing development of their WW2 military designs.

I think that post war, people were still trying to absorbe the jet concept...a flying wing was a bit much. Think of it along the lines of Udet, who did not trust a jet engine and made that sentiment known when he was shown the He178 for the first time.

 

[Gixxerman]

The Argentinian Pulqui does tend to indicate that the Ta 183, like a lot of the 'Luft 46' stuff, just might not have been the immediate smash-hit some claim.
I suspect the Horten would have been similar.

There's a vast difference between a sketched prototype (like the Ta) or even an actual prototype (like the Horten) and a properly tested combat machine using brand new tech.
Nevermind one with properly understood worked out tactics for it's use (something the Me262 was, of necessity, having to make up as it went along).

Advanced ideas have a habit of taking time to implement properly effectively.

 

[drgondog]

The promise of the Flying wing was reduced Parasite Drag for greater range, payload and speed. The curse (still is ) is lack of stability and control, now achievable with extremely sophisticated Control System feedback managed by computer.

IMO the key 'secret weapons' were
Radar
Asdic/Sonar
Computational gunsights slaving fire control systems and gyro coupled computing gunsights for fighters.
Practical jet engines
Controllable ballistic missiles utilizing rockets
Bazooka/Panzerfaust
Proximity fuses
Long range/high performance escort fighters
Nuclear weapons

I know I missed some but each of the above were game changers and/or major force leverage's that when introduced, introduced a major upgrade to attack/defense.

 

[GrauGeist]

The Germans were also making a great deal of progress with guided munitions, too. One of the most notable, was the "Fritz X".

 

[bobbysocks]

MG34 and early MG42 had two-position trigger (single shot and full auto, not slower rate of fire), deleted on later MG42.

yep...just remembered the double trigger and got confused with CETME Ameli...which looks like the 34/42 style and had 2 rates of fire...by swaping bolts

 

[Gixxerman]

The Germans were also making a great deal of progress with guided munitions, too. One of the most notable, was the "Fritz X".

I agree, wire guided missiles would become ( to some extent still are) very important munitions. But it's the usual story, too little far too late.
But I do agree, they were pioneering the field.

Perfected in the anti-tank role they might have gone some way to stop the sea of T's, KV's, JS's Su's heading Germanys way.
Unfortunately as far as air-launched weaponry goes even if they were available say a year earlier than they were scheduled to start arriving (June/July 45?) they were just too late would have been stuck with launch-vehicle problems (too few, little fuel too few pilots especially) not to mention skies crawling with so many allied fighters catching them taking off or landing (bit like the Japanese Ohka, an interesting deadly suicide bomb without a credible delivery means).

 

[Token]

IMO the key 'secret weapons' were
Radar
Asdic/Sonar
<snip>>

RADAR and SONAR are often quoted as WW II developments or secret weapons of WW II. Yet neither were. Important, yes, secret in detail (as many are today), yes, improved immensely during WW II, yes. But an invention of or as a result of WW II, no.

Both Axis and Allies used and developed SONAR and RADAR before and during WW II. And they knew of the use and development of SONAR and RADAR by the other side.

ASDIC / SONAR was developed in WW I. The state of the art from 1919 to 1940 changed little, but the systems did exist. In WW II they really became good systems.

RADAR is sometimes stated as a "British invention", but this is not true.

The basic principles of reflecting RF off of a target, such as a ship, to detect its presence goes back to before WW I and was the subject of many experiments in many nations. From the late 1920's to the late 1930's the associated technologies matured enough to support more research into this. This happened more or less concurrently in several nations around the World, including the UK, the US, Russia, Germany, Japan, Italy, France, Netherlands, and others. Every one of these nations had at least prototype working RADAR systems before 1940, and most had them before 1938.

The British where, by a very small margin of time, the first to successfully show what could be called "modern" RADAR in mid 1935 in a repeatable fashion. The US Navy had done essentially the same thing several months earlier (Dec 1934), but had problems repeating the experiment, and the detection ranges were much shorter. About 11 months after the British, and independent of them, NRL had their first operational and repeatable RADAR prototype that had been demonstrated to detect aircraft at significant distances.

The Japanese were arguably ahead of the rest of the World with regards to early RADAR antenna design and magnetron design, at least prior to the widespread use of microwave frequencies. And while they had operational RADAR systems during WW II they never seemed to embrace the technology as the force multiplier it can be.

T!

 

[pbehn]

For Radar the "invention" was the oscilloscope and the electronic gubbins. It had been noted that aeroplanes interfered with radio waves for years all that was needed was to see if anything was reflected and magnify it and make sense of it et viola RDF (radar).

 

[parsifal]

For both radar and asdic, it was not the invention itself that was the secret. Both sides knew of it, and in some respects the germans were technologically superior to the allies. The secrets were the manner and ways that these devices were used, and put simply the allies just put the hammers dowen and were never seriously challenged in either of those fields. Japan and italy, for example,. were about 5-10 years behind the allies in the development of radar, mostly because of an under-developed electronics industry.

Germany too, whilst enjoying an impressive R&D base for the technology never came close to the application of radar as the allies did. Sonar for example, the allies managed to solve its blind spot problems by 1943, which married to the ahead throwing technologies developed in the mid war period, really went a long way to defeating the U-Boats

 

[pbehn]

As I said, the "invention" is turning a wave into an electronic pulse, link that to a timing device and you have the basis of many technologies. I was an ultrasonic technician for a while, I was taught by one of the pioneers of ultrasonics in the UK. He ran the school in his home (a massive garage conversion) and still had 1950s ultrasonics sets there, they were very similar to what you see in the Battle of Britain movie.

Not an invention at all or even a weapon but a "key strength" for the allies was the obtaining and processing of information and intelligence quickly. That goes from Dowdings integrated defence of the UK, to the massive joint effort in aerial photo and weather recon over Europe, the ultimate being Bletchley park and all the services around it. I read that the Germans were not really surprised that enigma was broken, they were very surprised at it being broken on an industrial scale almost in operational real time.

 

[Ascent]

My understanding (and I could be wrong here) was that another key strength of the Allies was putting the technoligies into use.

The Germans tried to perfect it before putting it into use whereas the Allies would cobble something crude together that could be used while they worked on better stuff for the future.

 

[fastmongrel]

My understanding (and I could be wrong here) was that another key strength of the Allies was putting the technoligies into use.

The Germans tried to perfect it before putting it into use whereas the Allies would cobble something crude together that could be used while they worked on better stuff for the future.

The Germans were very dimissive of a British mobile radar they captured in France. The German radar experts called it crude and poorly made compared to German radars. This opinion ignored the fact that Britain had dozens of mobile radars plus a complete early warning and control radar system in the Chain Home, whereas Germany had a grand total of eight land service radars and they were being used for training and experiments.

A breadboard rig in the field is worth any number of radars that can't be used.

 

[pbehn]

The Germans were very dimissive of a British mobile radar they captured in France. The German radar experts called it crude and poorly made compared to German radars. This opinion ignored the fact that Britain had dozens of mobile radars plus a complete early warning and control radar system in the Chain Home, whereas Germany had a grand total of eight land service radars and they were being used for training and experiments.

A breadboard rig in the field is worth any number of radars that can't be used.

I agree.

You could say that Chain Home was 1936/7 technology in 1940 true but that is what time it takes in peacetime to get something out of a lab and working all around the country. By 1940 the British were working on airborne radar so cant have been far behind the Germans,

Dowdings control system with Chain Home contained no marvellous technology in 1949 just the imagination to link everywhere up by telephone and sort the information quickly so the guys in charge knew what was happening.

Maybe the flying wing was a great theoretical idea that didnt overcome many practical problems.

 

[Token]

My understanding (and I could be wrong here) was that another key strength of the Allies was putting the technoligies into use.

The Germans tried to perfect it before putting it into use whereas the Allies would cobble something crude together that could be used while they worked on better stuff for the future.

I think your first statement wraps it up well, but your second is a common misconception.

The Axis forces seem to have never put the emphasis on these kinds of technologies that the Allies did. Possibly this was not a weapon in the traditional sense, and so it did not "fight" the war, and more effort went to things that went fast and caused a bang.

The Allies radar in WW II was neither crude (for the time) nor cobbled together. They were developmentally ahead of the curve in relationship to the Axis in every way in the field of radar from about 1936 on, despite everyone being on pretty even footing in about 1934.

For example, the German Seetakt, Freya, and Wurzburg, radars were the equal to or even slightly ahead of their operational Allied counterparts on the days of their individual introduction to operational service. They were not ahead of what the Allies had in development and prototyped. The Germans used these radars by the thousands, and made gradual improvements to them along the way.

The Allies made the CXAM/SCR-270/271 and SCR-268 (these compared well to the Seetakt and Freya at the time of their introduction) and used them by the thousands. Instead of making large improvements to these radars the efforts tended to be more minor improvements, and "lets build a new radar while we keep these models in operation". They developed a good radar, fielded it, and instead of improving it (other than required improvements to correct deficiencies) they continued its production while starting up more advanced programs in the background. Remember the SCR-270 detected the Japanese raid on Pearl Harbor on the way in with lots of warning time, but that information was not used / interpreted correctly.

By 1943 the comparative acceleration rates of the Axis and Allies in this field was pretty obviously leaning towards the Allies. The Germans were largely maxing out the ability of their existing systems, with few new systems fielded in any number, and the Allies were introducing whole new systems with new technologies. An example of this: what would become the SCR-584 started development roughly one year after the Wurzburg development started, and was operational by early 1943, 3 years after the first Wurzburg. It took longer to develop because it was doing new things in new ways. This effort paid off handsomely, as the -584 was far superior to the improved Wurzburgs of 1943. The -584 was trailer mounted and could be quickly set up (in minutes) in a new location. The -584, despite having a more compact antenna, had greater tracking accuracy. The -584 had search modes the Wurzburg did not have. The -584 had the ability to automatically track a target, were the Wurzburg was an operator intensive aided / manual track. The -584, with the M9, resulted in greater gunfire accuracy for larger numbers of guns.

The SCR-584 was in its spring with lots of headroom to grow at the same time the Wurzburg (and similar German systems) was in its fall. While aspects of the Wurzburg designs were used in very limited numbers after WW 2 the SCR-584, in various incarnations, is still in use today. The Russian built Fire Can radar (SON-9) was a copy of this radar developed from the SCR-584's given to Russia during Lend Lease and is likely still in use with several militaries around the world. It was for sure shooting down American aircraft as late as 1973.

The last time I personally had hands on an operational SCR-584 was in the early 1990's.

T!

 

[Koopernic]

I think your first statement wraps it up well, but your second is a common misconception.

SNIP
The Allies radar in WW II was neither crude (for the time) nor cobbled together. They were developmentally ahead of the curve in relationship to the Axis in every way in the field of radar from about 1936 on, despite everyone being on pretty even footing in about 1934.

For example, the German Seetakt, Freya, and Wurzburg, radars were the equal to or even slightly ahead of their operational Allied counterparts on the days of their individual introduction to operational service. They were not ahead of what the Allies had in development and prototyped. The Germans used these radars by the thousands, and made gradual improvements to them along the way.

The Allies made the CXAM/SCR-270/271 and SCR-268 (these compared well to the Seetakt and Freya at the time of their introduction) and used them by the thousands. Instead of making large improvements to these radars the efforts tended to be more minor improvements, and "lets build a new radar while we keep these models in operation". They developed a good radar, fielded it, and instead of improving it (other than required improvements to correct deficiencies) they continued its production while starting up more advanced programs in the background. Remember the SCR-270 detected the Japanese raid on Pearl Harbor on the way in with lots of warning time, but that information was not used / interpreted correctly.

By 1943 the comparative acceleration rates of the Axis and Allies in this field was pretty obviously leaning towards the Allies. The Germans were largely maxing out the ability of their existing systems, with few new systems fielded in any number, and the Allies were introducing whole new systems with new technologies. An example of this: what would become the SCR-584 started development roughly one year after the Wurzburg development started, and was operational by early 1943, 3 years after the first Wurzburg. It took longer to develop because it was doing new things in new ways. This effort paid off handsomely, as the -584 was far superior to the improved Wurzburgs of 1943. The -584 was trailer mounted and could be quickly set up (in minutes) in a new location. The -584, despite having a more compact antenna, had greater tracking accuracy. The -584 had search modes the Wurzburg did not have. The -584 had the ability to automatically track a target, were the Wurzburg was an operator intensive aided / manual track. The -584, with the M9, resulted in greater gunfire accuracy for larger numbers of guns.

The SCR-584 was in its spring with lots of headroom to grow at the same time the Wurzburg (and similar German systems) was in its fall. While aspects of the Wurzburg designs were used in very limited numbers after WW 2 the SCR-584, in various incarnations, is still in use today. The Russian built Fire Can radar (SON-9) was a copy of this radar developed from the SCR-584's given to Russia during Lend Lease and is likely still in use with several militaries around the world. It was for sure shooting down American aircraft as late as 1973.

The last time I personally had hands on an operational SCR-584 was in the early 1990's.

T!

Deliveries of Wurzburg D to the Luftwaffe started in June 1941. It gave the Luftwaffe a radar with 0.3 degree accuracy elevation/azimuth accuracy with conical scan and 25m accuracy in range with transfer to the FLAK predictor by Synchro. These figures assume a high elevation angle so that there would be no interference with the ground plane otherwise 0.5 degree and 40m. This was the finest anti aircraft gun laying radar in the world till mid/late 1943 when SCR-584 was rushed to Anzio Beachhead because the Germans were jamming the SCR-268. There was nothing like it in the allied arsenal for 2 years. Wurzburg-Riesse, with a giant 7m dish had twice the angular accuracy again and when this fixed radar as a FLAK radar was a very accurate blind fire radar to defend cities and high priority targets. Wruzburg-C (early 1941) had the conical scan but lacked the range precision and synchro transmitters and the Wurzburg-A of 1940 lacked the conical scan entirely.

SCR-268 was 2.5 times less accurate in bearing accuracy and 3.5 times less accurate in range to Wurzburg-D. That made it essentially ineffective for pure blind fire.

Around late 1943 as SCR-584 was entering service the Germans introduced the Mannheim FuMG 64 radar. As it also had a 3m dish it is often confused with Wurzburg. Output power was doubled, power drive was added, precision electronics for tracking was added and range accuracy was 10m. The second issue of this radar of early 1944 added electronic tracking and reduced ranging precision to 6m. It could track through windows once a target was found.

This radar compares very favourably with SCR-584. However the Germans had stayed on a 53cm wavelength instead of 9cm microwaves so there radar beam was wider and more vulnerable to receiving jamming energy.

In mid or late 1944 they field tested a few Rotterheim radars consisting of LMS10 magnetrons (copied from captured British CV64 but set to 8.4cm instead of 9cm to avoid interference with German passive detectors) using a Mannheim station and a Wurzburg dish. Worked quite well and was not jammed. However by late 1944 the war was going badly. The Sanitas works that made the Magnetrons was bombed and so the Germans lost all of their mass production output of magnetrons. The Hareaus Vacuum Foundry was bombed which means they lost their capability of producing permanent magnets and forcing them to modify the magnetrons for electromagnets and adding an unwelcome precision power supply.

This pretty much destroyed the deployment of microwave radar for the Germans though they managed to get up to 100 in service including on naval installations.

Below is a picture of the Marbach Egerland radar system. The flat antenna is a PPI 8.4cm microwave radar. The parabolic dish was a 4.5 m dish also on 8.4cm. The PPI radar could observe multiple targets. A pip could be placed on a target and the parabolic dish would slave to the correct direction and scan for height. Up to 7 targets could be tracked. The parabolic dish could also direct FLAK. Power output was only 16kW but 500kW and 1MW magnetrons were in the lab.

As far as Seetak goes this was the finest radar of its type till about 1943 as well and matched allied systems till the end of war.

Early versions had only 1.5kW output power, they then switched to 8kW power and shortly thereafter added what is incorrectly called lobe switching for full blind fire capability (about 0.2 degrees) it seems in 1941 on FuMo 27. Whereas the lobe switching of American Battleship and cruiser radar switched both the transmitting beam as well as the receiving the Germans had worked out a way of switching only the receiving dipoles in a procedure call raddle peilung (rattle direction finding) named after the rattling sound made by the mechanical switch of the receive dipoles. This reduced the beam width, hid the lobe switching pattern from jamming techniques and made the antenna smaller. The lobe pattern on US Battleships was so wide (15 degrees) it could confuse nearby targets.


The whole Scharnhorst sinking reinforces the myths. The Scharnhorst was observing radar silence and passive sensors had mistaken Burnets cruisers for a distant convoy though a short 30 second 'action stations' was sounded indicating the Scharnhorst had detected them probably by passive means. The short fire fight damaged Scharnhorst forward radar meaning she was no longer able to detect Duke of York in the latter encounter though again there was an action stations before DoY fired.

The German radar was 8kW at the time and was equal in performance to the British 25kW radars. The Germans had a much longer pulse of lower peak power so the range was about the same since the energy was the same. Because they used grid instead of anode modulation they could synchronise the phase of the transmitter to receiver and recover phase information for recovering resolution and accuracy. In the case of Duke of York the Type 284M radar had just been upgraded from 25kW to 125kW so the British were now outranging the Germans. The rear facing German radar could probably detect and range the British ship but at long range it probably couldn't pick up shell splash which is needed for correcting fire. At one point the Duke of York had to stop firing because it couldn't pick up shell splash as the range opened up. Scharnhorst was 50% of Germanys capital ships and was not quite the radar priority but they had planed to upgrade to 120kW power.

On the day she was sunk Tirpitz detected the Lancasters 30 minutes out at 150km over land using her own radar. This long range indicates she had been upgraded to 120kW. She also had a Hoehtenweil PPI radar added by then and a FuMo 81 Berlin 9cm microwave radar. If Tirpitz had of ended up in one of those Iowa/Missouri fights the Tirpitz would not have been outperformed in the radar area. (To be fair H class battleship is same Generation as Iowa)

The failure to intercept the Lancasters is now thought due to treachery as the commander of the German Wassermann radar station which had detected the Lancasters was a traitor along with two colleagues they misreported the Lancasters heading. The men were latter extracted by Norwegian resistance and had planned to shoot their own officers and surrender in case of an allied invasion thus proving they had turned.

Me 109's were scrambled but were delayed further by 5 minutes due to a Ju 52 transport landing and a few minutes by being dispersed at the wrong end of the runway due to headwinds. They missed the Lancasters by 2 minutes.

 

[parsifal]

Its silly to argue that german radar at sea in 1943+ was equal or superior to that of the allies. By 1943 their surface fleet was largely laid up in ports with occasional heroic, but futile sorties that at no point showed any marked or clear superiority in terms of the detection systems they carried. In terms of ground based radars it might be a different story, but at sea , there is no instance after 1943 that demonstrates a clear superiority of german surface air search or fire control radars.

Overwhelmingly, the main battle at sea with the Kriegsmarine throughout the war, but moreso after 1942, was with the Uboats. Allied small ships possessed radar capable of detecting a Uboat periscope from 1941. They possessed an ASV set with an effective range able to detect a perisope at ranges out to aboput 5miles from the end of 1942. by 1943, the Uboats, whilst belatedly being fitted with a surface radar, were hopelessly behind the allies in terms of what they could stuff into a small package and make it reliable enough for operational use in a heaving Uboat. They did do it, and it worked, but it was nowhere near as effective as the allied short wavelength surface and airborne radars being fitted into allied warships and a/c at that time, and which they found themselves facing up to. if they had been equal to the task, it becomes impossible to explain why in the space of less than 60 days in 1943 they lost more than 60 Boats. If their radar had been equal or superior to the late war allied suite, the slaughter of their kind could not have been achieved.

The Kriegsmarine was in fact investing in passive detection systems, namely Metox and Naxos. For a time these passive detectors gave the Uboats early warning of allied active radars, but they were sucessively countered and overcome by the allies each time.

Germany had some very superior radars in development in the latter part of the war. Several of her ships were fitted with these radars, but standing operating policies largely negated the advantages these modern radars might otherwise have given

 

[nuuumannn]

Regarding radar, you could be a bit more specific and argue the case for the cavity magnetron.

 

[Koopernic]

Everyone in the world was aware of type of magnetron called a split anode type, roughly could be regarded as having two semi circular cavities. The Germans used one in 1935, quite successfully, on their testbed seetakt.

The British invention consisted of 6 multiple cavities that were round and had a narrow slit. The dimension were exactly that of a 0.38 inch revolver and indeed were made on tools for that revolver. More powerful at high frequencies.

The early British microwave radar had considerable limitations in accuracy because of the way the pulse is formed. These problems and the problem of detecting shell splash meant the RN never abandoned its type 284 nor did the USN (and they fixed the beam width issue). However they could be installed on small escort corvettes where they had separate transmit and receive antenna and had to use coiled up coax cable. I was very primitive, no PPI for instance and inaccurate but sufficient for detecting u-boats. PPI took a long time to be issued probably late 1943 as the priority was H2S. Seetakt from the very beginning of war could be fitted to a destroyer due to its refined antenna technology and relatively high frequency. Remember the microwave radar never led to a deployable British microwave Anti Aircraft radar, there was some Canadian work, for the British and the American work wasn't ready till 1943 either.

Hence the Germans didn't have so much incentive to develop a crude microwave system as their systems worked quite well. It wasn't until mid 1943 with the deadly Hamburg fire bombing where windows was used and which that killed 40,000 people that the worst problem became apparent. IE with reasonable sized antenna the beam width intercepted to much jamming energy.

The key features of the British invention were understood by the Germans. Multiple Circular cavities with narrow slits was a feature of a German magnetron of 1940 by Lorentz. If you have $25 you can download the paper by Doering on German microwave tube development which has a picture. It was however designed for generating small signals only. A larger tube by Santias, also from 1940 good for 200W continuous and probably 2kW pulse had all the features but the circular cavities, they were square. The French experimental 16cm radar was based on this square cavity type of multicavity magnetron and some features of its emissivity coatings ended up greatly improving the British tube.

The German quest for higher frequencies was directed at developing highly refined existing technology. Although they had developed the tubes required which were known as ceramic disk triodes (lighthouse valve in the US). with this they produced a 5.5kW 21.5cm radar in 1940 called eisbaer (ice bear or polar bear) and had planned on deploying a FLAK control radars in about 1943 at about 27.5cm. The set was called Mannheim-K to operate at 120kW, a 50kW version for fire control with a reduced size antenna was probably deployed at the end of the war, It was called Euklid. Lorentz's was described as 80cm complete in 1942.

One reason for these systems is that the Germans had developed a habit of using one advantage of these 'triode' devices in that the frequency and phase could be precisely controlled and they were keen not to give it up leading them to focus on difficult and complex devices.

Due to resource issues and the problems of setting up new production lines these efforts were mostly abandoned just development of fieldable devices seemed imminent. The technicians were drafted into the German armed services. A engineer called Peter Schwann who emigrated to the US is interview by the IEEE and he notes it took months to get the experts back from the field after the British magnetron was discovered in a shot down sterling.

Using engineers technicians and engineers in front line units was very common for the Germans. Combat exposure was highly expected and skilled men were sometimes rotated back and forth between industry and the services. Apart from the obvious disadvantage of plundering German industry of its skilled manpower these men often were captured and so were an enormous intelligence risk.

The manpower shortage can not be underestimated. Nevertheless German radar was as good in some cases better till 1943 when the superiority of microwave systems showed up in some critical areas. The Germans did effectively catch up technically in 2 years and field devices within 1.5 years. There is a statement by one of the British radar developers tasked to analyse the German development (Lovell I think) and he says they had essentially caught up and that the advantage of radar would now switch to the defenders.

The Japanese actually beat Randall and Boot to a magnetron by 1 year. The tested their surface search sets on a pair of cruisers around then same time. They however only slowly rolled it out and then only in the navy. Nevertheless their Type 22 was an effective surface search radar and there would be no sneaking up on them. They only developed it into a blind fire radar right at the end of the war.