The codebreakers of the Foreign Ministry – Pers Z succeeded in solving the main Polish diplomatic code in 1940 so messages in 1941-42 were read almost 100%.This is the relevant part from TICOM I-63 ‘’ Interrogation report on ORR Hermann Scherschmidt of Pers Z S Auswaertiges Amt’’ p2
Scherschmidt worked entirely on diplomatic traffic and was not familiar with military or agent systems or with any successes achieved on them. He had dabbled in Polish throughout his Pers Z S career and early in 1939 he was assigned to the main diplomatic code of the Polish Foreign Office. This had been in force since 1934, and some unsuccessful research had been done in an effort to ascertain the encipherment used. The problem was given a very high priority in 1939 and Scherschmidt had first class assistance. With the aid of a captured specimen of encipherment and a captured description of the indicator system, the first message was read early in 1940. The code was recovered gradually, and in 1941 and 1942 all messages was read, most of them currently. The code went out of use in October 1942 and was replaced by a letter code. Scherschmidt did a little work on this at first but did not come back to the problem later. He said the code was never solved, and he did not know details of the attacks made on it by KUNZE and others.
The new version was not solved by the Germans.However that was not their last success with Polish systems.Huettenhain ,chief cryptanalyst of OKW/Chi, solved a system used in diplomatic links by the Polish Ministry of Interior and for military attaché traffic.I’ll write about that case in a future post.