However there is one thing about this affair that still bugs me. The German solution of the strip system was facilitated by the material they received from their Japanese allies.
Agents of the Japanese Military Police were able to enter the US consulate in Kobe in late 1937 and they copied the 0-1 ‘circular’ set of alphabet strips. This was used for communications between embassies and for messages from Washington to all embassies. This material was shared with the Germans in 1941.However this material was not the only set of strips that the Germans were able to acquire covertly. Dr Wolfgang Franz, who was responsible for the strip solution at the German High Command’s deciphering department – OKW/Chi, said in his report TICOM DF-176, p6:
‘Especially laborious and difficult work was connected with an American system which, judging by all indications was of great importance. This was the strip cipher system of the American diplomatic service which was subsequently solved in part. After I had been working on it for a long time and was beginning to get some insight into the system, the work was greatly furthered by some captured material. This was given to me with no word as to its provenance. From inscriptions and notes, however, one could infer that these were Japanese photographs. These were the basic material of the so-called ‘intercommunication strip cipher system 0-1’ and three further sets for special circuits between the Department and Reval, Tallinn and Helsinki (?) with designations of the type 19-1 or something similar. With these, several older messages could be read and the door was opened for further study of the system.’According to David Kahn in ’Finland's Codebreaking in World War II’ in ‘In the Name of Intelligence: Essays in Honor of Walter Pforzheimer’:
‘The Finns got their break into the strip system when the German military espionage agency, the Abwehr, whose chief, Admiral Wilhelm Canaris, was a friend of Hallamaa, gave them photocopies of instructions for the strip cipher and of the strips for Washington's communications with the posts at Riga (which had been closed since June 1940) and Helsinki, as well as the 0-1 set.’How did the Germans get hold of the strips for Riga, Tallinn and Helsinki? From what I’ve read the Japanese were the source for the 0-1 set not the rest.
The strips from the embassies of the Baltic countries could have a connection with a Finnish civilian plane shot down by the Soviets in 1940.The Kaleva was a Finnish civilian airliner that was shot down by Soviet planes on June 14, 1940, while en route from Tallinn to Helsinki.
Onboard was a US diplomatic courier, mr Henry W. Antheil, Jr who was apparently carrying diplomatic pouches from the U.S. legations in Tallinn and Riga. According to the wikipedia page the plane crashed at sea and the first on the scene were three Estonian fishing boats. Then a Soviet submarine reached the location and recovered all the material from the Estonians. This amounted to:‘about 100 kg of diplomatic mail, and valuables and currencies including: 1) 2 golden medals, 2) 2000 Finnish marks, 3) 10.000 Romanian leus, 4)13.500 French francs, 5) 100 Yugoslav dinars, 6) 90 Italian liras, 7) 75 US dollars, 8) 521 Soviet rubles, 9) 10 Estonian kroons. All items were put on board of patrol boat "Sneg" and sent to Kronstadt’
So the question remains. If the alphabet strips from the Baltics were recovered from the Kaleva plane, who got them and how did they end up in German hands?Perhaps the Estonian fishermen were able to search the diplomatic bags and they retrieved the cipher material. Then when they got back to Estonia they could have given these to the military authorities who in turn shared them with the Germans.
That’s one theory.Another one could be that the Soviets after recovering the diplomatic bags searched them thoroughly and recovered the alphabet strips. If that was the case then how could the Germans have gotten hold of them?
Could there be an exchange of secret material between the intelligence agencies of Nazi Germany and the Soviet Union? In the period 1939-1941 they were officially ‘allies’….Quite a mystery!