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Chi Stelle (Air Force)

The largest and newest German Signal Intelligence service was that of the Air Force. The newly established Luftwaffe relied on the Army for its signal intelligence needs for the first few years, but then established its own service on January 1, 1937,  the Chi Stelle, OB d L. Starting with one officer and twenty civilians, it grew into an intelligence force of 13,000 by 1945. Its outstanding achievement during the war was what TICOM described as ‘….signal intelligence without cryptanalysts’. Its skill in interception and traffic analysis enabled the Chi Stelle to exploit all sorts of Allied radio emissions; radar, navigation beacons and radiotelephone chatter, which created a reputation for yielding valuable tactical and strategic intelligence. For instance, as early as December, 1939 Chi Stelle units detected a large formation of British Wellington bombers over Northern Germany and were able to provide the location, height, speed and size of the formation to the defending Luftwaffe fighters. This taught the Germans that signal intelligence would play a critical role in air raid defenses.


The Air Force Sigint service paralleled the army service in that it had a central analysis and administrative center, the Chi Stelle, located in Potsdam. At the start of the war, it had 10 mobile intercept companies and 14 fixed intercept stations under the cover of “weather stations”. As the war progressed, the Luftwaffe organized radio reconnaissance battalions for each air fleet supported by a fixed station back in Germany. Eventually the field service was organized into three radio reconnaissance regiments; the 351st covering the western front, the 352nd in the Mediterranean and the 353rd in Russia.  The Chi Stelle headquarters in Postdam was designated the 350th Battalion and was divided into a number of geographic evaluation sections along with its administrative departments.  Following the German decentralized philosophy, the Chi Stelle sent a number of detachments forward to support the field forces, and TICOM concluded ‘…it was considered more effective to have the long-term evaluation center close to the intercept units rather than close to the staffs which they have to feed.  However, as the war drew on, all of these detachments eventually merged into evaluation companies for the Air Signal regiments and battalions they served.

Courtesy of LA6NCA/FYKSE 

The cryptanalytic effort on the Russian front was almost entirely field based, with 85% of the low and medium grade Russian systems read. The nature of air warfare required a rapid intelligence response, with results needed in a matter of hours rather than days or weeks as with the ground forces. Despite this level of cryptanalytic success with the Russians, the Chi Stelle failed to solve other enemy high-grade systems such as SIGABA or Russian one-time pads.


Facing the much more difficult cryptanalytic challenge in the West, the Chi Stelle relied heavily on interception and traffic analysis for rapid response. The Chi Stelle and its field tactical units became the prime source of intelligence for the Air Raid Warning Agency of the Reich, a function that became critically important as the Anglo-American bombing campaign developed in 1943-45. They developed sophisticated techniques for intercepting Anglo-American radar and navigation systems. Eventually the Germans were able to track the exact strength, composition and probable targets of enemy bomber raids in near real time.  David Kahn concludes:

“German air force radio reconnaissance gave advance notice of many Allied raids, and indeed provided 70 percent of and the most valuable intelligence about the enemy that the Luftwaffe received. But German flak and fighters were often too weak to do much against the broad and endless stream of Allied bombers. In the end, air radio intelligence did little more than to prove once again that knowledge without power is worthless.”


Nevertheless, not all signals intelligence success in the west was due to traffic analysis. Chi Stelle assisted in the breaking of the M-209 machine cipher and by spring of 1944, the GAF was reading 6-8 days of encrypted traffic per month. Their reading of M-209 traffic from the US XXIX Tactical Air Command tipped off the Germans to a planned ground offensive in the Aachen area. In addition, many low-level strip systems of both the USAAF and the RAF were read, including aircraft movement codes and bomber codes.
Conversely, on the eastern front, Air Force Sigint could be of great help to the Army. The Russians had a practice of following radio silence prior to a major offensive, their attached air armies however, had to continue to coordinate in order to both move their forces and operate their aircraft. This allowed the Luftwaffe signals intelligence service to tip off their ground colleagues to be prepared.


Decentralization however created problems for the Chi Stelle. Although it permitted flexibility and an emphasis on tactical intelligence, it diluted any coordinated approach to attacking the high-grade strategic systems of the enemy and the cryptanalysts resented their lack of ability to control intercept targets, which denied them the amount of traffic they needed to work on specific systems. The Luftwaffe signals intelligence effort was under the control of the Chief Signals Officer rather than the intelligence chief, and this created some problems in coordination and emphasis.
After a number of reorginations, by late 1944, the Air Force SIGINT service was placed under a Senior Signal Intelligence Officer, Generalmajor Klemme, a veteran signals officer. He was aided by his operations officer, Lieutenant Colonel Friedrich,  who had direct command of the  350th Battalion, the Chi Stelle. Friedrich was a general staff officer and had no background in signals, a fact that later created problems as he struggled to keep up with a fast changing , highly technical field. Klemme and Friedrich were captured separately by the British in May 1945. Friedrich  was flown to the UK to be interrogated and Klemme ended up working for the British until 1948.
 TICOM had no contact with the Chi Stelle during its search, although Team 2 explicitly looked for Regiments 350 and 351 in the Imst area. They concluded that the personnel of these regiments probably donned civilian clothes and went home. Most of TICOM’s information on the Chi Stelle came from prisoners’ interrogations, captured documents and study of a 13-volume report from the USAAF known as the “Seaborne Report”, along with some British sources. Among the prisoners, Lieutenant Colonel Friedrich, Dr.Voegele, Chief Cryptanalyst, Lt. Ludvig, chief evaluator on the western  front, and Major Felchtner, Commanding Officer of Air Signals Regiment 352 became primary sources of information for TICOM.



European Axis Signal Intelligence in World War II.... Volume V: The German Air Force Signal Intelligence Service.

TICOM Team 1 report on the OKL Headquarters.

TICOM D-79 Organization of GAF Signal Service, Including the GAF Signal Intelligence service, Part 1 Part 2,   Part 3.

Cryptanalysis in the German Air Force by Oberleutnant Waldemar Werther.



David Kahn, Hitler's Spies. Cambridge, MA: Da Capo Press, 1978.

Subpages (1): Related Reports