Invasion of Sicily
In July 1943 US and British troops invaded the island of Sicily and after more than a month of fighting defeated the Axis forces and captured the island. However the German forces were able to avoid a total defeat by retreating in an orderly fashion through the Strait of Messina.
It seems that during the fighting in Sicily the Germans managed to capture a valid keylist of an M-209 network and thus read current US military traffic (14).
The war diary of Inspectorate 7/VI says that in July ’43 the captured material allowed the continuous decryption of the traffic with indicator ‘ID’ and the results were communicated to NAAst 7.
The report of August ’43 says that messages of the ‘ID’ network could be decoded till mid month and after that it was still possible to find several cases of indicator reuse and thus solve the traffic of those days cryptanalytically.