They're distributing the attack surface by using other services.
They're distributing the attack surface by using other services.
Also, nothing stops you from redistributing the structured messages through multiple channels.
As a military, you never want to give that away. Looking at WWII, the UK/US were able to decrypt messages daily from the Germans (thanks to Turing!), but they pretended they couldn't so the Germans wouldn't change their encryption scheme.
Turing's methods are brilliant as are the contributions of numerous other cryptographers. They relied on numerous operational failures of some branches of the military to be possible. So it was not from "the Germans", but from specific branches of the military that failed to follow already established best practices
https://www.accuweather.com/en/weather-news/how-british-cryp... gives a pretty decent summary.