> Research seems to indicate that over one-third of the tanks used by the Russians in defence around Moscow during Barbarossa (in Dec 1941) were British:

I didn't know this, but I don't find it astonishing. This was when Russia was losing and the defense of Moscow was pretty desperate. It's likely a lot of those British tanks were lost during that battle (as noted, they weren't very good) and replaced with T-34s.

It's worth noting that most of the recorded losses of tanks by the Germans were in battles against T-34s.

> It's worth noting that most of the recorded losses of tanks by the Germans were in battles against T-34s.

Russia had to first survive long enough to get things turned around so they could take the offensive.

On the T-34s:

> To the Deputy People's Commissar of Medium Machinebuilding, comrade Goreglyad 8a Ryazanskaya St.

> In response to your letter #16/2291 on March 18th, 1941

> The GABTU considers it necessary to deliver the V-2-34 engine together with the main clutch for the following reasons:

> The warranty period of the main clutch is seldom higher than the lifespan of the engine: the engine's guaranteed lifespan is 150 hours, the tank travels 2000-2250 km in this time. The existing main clutch needs replacing after this time.

> The existing design of the main clutch on factory #183 T-34 tanks requires the following changes to be compatible with diesel engines received from factory #75:

[…]

* https://www.tankarchives.ca/2020/12/weakest-link.html

* https://twitter.com/Tank_Archives/status/1344342553911582722 (see thread on Kursk)

When the average lifespan in battle was ~14 hours, the stated 150 hours sounds pretty good.

Worth noting that (again) logistics are the important factor. Tanks might survive 14 hours in battle, but spend much longer getting there (and there weren't often tank transports available outside railways).

British intelligence, Bletchley Park aside, was amazingly ham-handed and ineffective, by accounts of those involved. (See Leo Marks, "Between Silk and Cyanide".)

The US, incidentally, was able to decrypt Enigma traffic independently of Bletchley using ordinary cryptanalysis.

The US seems to have used its own equipment, but used British cryptanalysis:

* https://en.wikipedia.org/wiki/Cryptanalysis_of_the_Enigma#Am...

* https://en.wikipedia.org/wiki/Bombe#US_Navy_Bombe

Do you have sources that indicate otherwise?

I rely on a biography of the Friedmans.

No mistake, they had full access to the Polish analysis and bombe design.

These were not used in the most critical battle of the war, that unquestionably resulted in a massive battlefield victory that changed the course of world war 2 - Midway.

Japanese codes were transparent before and throughout the war. They were not Enigma codes.

It was well known exactly when the Japanese planned to start the Pacific War, though intercepts did not say where. Many in the Navy were sure it would be at Pearl Harbor. Notably, the militarily useless battleships were there, but not the aircraft carriers.

And all the mathematical breakthroughs needed to crack Enigma and make it tractable to the primitive computers of the day were made by the Poles anyway, which was conveniently airbrushed from history.

I was not aware - could you explain further?

Poles smuggled out a complete first-model Enigma machine, performed the cryptanalysis that revealed its core weakness, and also created the first of the "bombe" machines used for most of the decryptions.

Bletchley Park acted as central clearinghouse for intercepted ciphertexts, distributing decryptions with elaborate care to keep the Germans from knowing Enigma had been cracked. Late in the war, they built an electronic gadget called Colossus to decrypt traffic from a much more difficult version of Enigma.

The article that I cited also makes mention of this, along with a photo of British "Matilda" tanks being loaded for shipment.

"In addition, much of the $31 billion worth of aid sent to the United Kingdom was also passed on to the Soviet Union via convoys through the Barents Sea to Murmansk."