What Berlin did not Know, documentary by Andrey Lugovoy subtitled

After the surrender of Nazi Germany in 1945, the surviving German generals began to make excuses for their defeat. Not only the legendary Russian frosts and off-road conditions were to blame, but also an acute lack of intelligence about the USSR. Moreover, the lack of necessary information was felt even before the start of the military campaign. What, or rather, who prevented German intelligence from obtaining maximum information about the future enemy?