[antman]

They organized airplane flyovers that "saw" the U-boats. The Germans did not know how many aircrafts were patrolling and whether it was a high or low probability of being spotted.

If the British could not organize a parallel construction they simply let it go. They knew the plan for Crete invasion but they could not create a story on how they learned it so they preferred to lose naval control of the large part of the eastern Mediterranean sea. [0]

[0] https://www.amazon.com/Churchill-Secret-Service-David-Staffo...

[WalterBright]

The sub killers were waiting at meeting points for the U-boots and their "milk cows" so often that the obvious possibilities were:

1. the allies had enormous numbers of sub killers 2. the allies were incredibly lucky 3. Enigma was broken

Waiting for proof before acting is not a sensible decision.

(Even in WW1, the aviators regularly changed their codes used. They knew they were only good for a few days each.)

[empath75]

Let's imagine you've figured out that the codes were broken in Hitler's Germany. The only solution is replacing an expensive encryption system with another, equally expensive system, including all the training that goes along with it.

Who do you tell? And who is the guy that going to go to Hitler to tell him that their unbreakable system is broken?

[WalterBright]

You go to Admiral Doenitz, who already suspected it was broken, and was talked into not changing it by underlings, not Hitler.

BTW, my reading books about it suggests that one was not executed in the military for questioning orders. One reason the German military was so effective is much discretion was allowed by underlings, as well as listening to them.

[leoc]

I'm not well versed on the subject, but I assume it was just another of those large-scale intelligence failures, like the https://en.wikipedia.org/wiki/Englandspiel only with the boot on the other foot. Groupthink in action again. Also, given the large number of important ciphers which were broken during the war, I'd guess wildly that the pre-war crypto communities (such as they were) were generally much too complacent about the risks from cryptanalysis, likely because ciphers had never been subjected to state attack on a Manhattan Project scale before. Comparable to the long time it apparently took for people to become generally aware of C buffer overflows as a serious security problem, maybe.

[ISL]

5. There was a mole.

[Retric]

4. The US had some other means of tracking subs.

[WalterBright]

Not long range methods other than breaking Enigma messages which said where/when U-boots were to go. This is what made breaking Enigma so important.

[Retric]

That's what we actually did, however RADAR was a new thing allowing a small number of British aircraft to regularly intercept Bombers. Without any evidence it must have seemed probable for something similar to be locating subs.

[lostlogin]

Regularly intercept in daylight - it performed poorly roughy that at night interception rates were abysmal.

[Retric]

Detection worked just fine at night. The problem was: "Although the RAF control stations were aware of the location of the bombers, there was little they could do about them unless fighter pilots made visual contact." https://en.wikipedia.org/wiki/Radar_in_World_War_II

[lostlogin]

The codes were changed regularly but the system was compromised. Naval codes were harder to break and often the allies had long periods of being in the dark.

[dboreham]

4. Airborne Radar had been developed.

[adekok]

The British did significant amounts of data analysis and traffic analysis. e.g. estimating German tank production by looking at the serial numbers of captured / destroyed German tanks.

I don't recall anything about the Germans doing the same thing.

[funnyfacts365]

Ofcourse you don't. They lost. Winners write history as they want...

[mturmon]

Another factor (according to the excellent Battle of Wits by Budiansky) was that the Germans were overconfident that Enigma was unbreakable. Turned out their confidence in the hard computation that would need to be done to decode Enigma was wrong.