The Funkabwehr, "Radio Defence Corps," was a radio counterintelligence organisation created in 1940 by Hans Kopp of the Armed Forces High Command during World War II. It was the principal body for the monitoring of illicit broadcasts. Its formal name was Funkabwehr des Oberkommandos der Wehrmacht (German: Oberkommando der Wehrmacht, Wehrmachtnachrichtenverbindungen, Funküberwachung) (OKW/WNV/FU). Its most notable breakthrough occurred on 26 June 1941, when tracing teams at the Funkabwehr station at Zelenogradsk discovered the Rote Kapelle, an anti-Nazi resistance movement in Berlin, and two Soviet espionage rings operating in German-occupied Europe and Switzerland during World War II. The Funkabwehr was dissolved on 30 April 1945.

The Radio Defence Corps of the OKW was given the task of picking up and locating by Direction finding (DF) transmitters of secret agents and other clandestine 'underground' transmitters. An underground transmitter was the secret radio station established in enemy-occupied territory. Such a station was charged with passing back to its control station, information of a military, political, or war-industrial nature obtained through espionage. This facilitates the carrying out of pick-up missions. Underground stations also pass traffic relative to the administration and supply of secret organisations and resistance groups. An underground transmitter is usually one of several belonging to a more or less large espionage organisation.

The moment a clandestine transmitter sends treasonable traffic, it becomes an underground station. A method of discovering a secret agent and clandestine traffic, according to radio intercept procedure, and fishing it out of the mass of regular traffic was only possible when every intercept operator, or at least every analysis station, had access to the full spectrum table of all known radio traffic.

It was the duty of the Radio Defence Corps to build up this spectrum table of recognised traffic, by working it out by all the organisations concerned. When all unaccounted traffic had been DFd, the underground station was exposed. The DF of underground and clandestine transmitters had to be accurate enough so that, on the basis of the bearings alone, the station was located and destroyed. By DF and Radio Intelligence, it could be determined what espionage cover-organisation each transmitter belonged to. By deciphering intercepted traffic of a given station before its extirpation, the following actions are undertaken by units of the Funkabwehr.

By exercising rough DF-ing of the underground transmitter, the following could be accomplished:

In the event that a so-called G-V Game, i.e. playback, was to be carried out, the Funkabwehr conducted the technical execution, while the information to be contained in the messages was furnished by the head office of the Reich Security Main Office, or Military High Command. To carry out a G-V Game means to have a captured enemy agent continue operations against the parent service which they had been previously operating. The fact that they are doing this must not become known to the original parent organisation. If the G-V Game was well carried out, it was possible to enter deeply into the parent organisation, such that the parent can be broken wide open. A good G-V game enabled future military organisations of the parent to be determined.

G-V Games in general could only be carried out when:

The Funkabwehr developed out of the (German: Horchdienst) or Listening Service, which was the German interwar radio intelligence and interception service, that was later expanded by the Funkabwehr, the Luftwaffe and the General der Nachrichtenaufklärung, early in the war, until by 1942, each service had an independent interception organisation. The Funkabwehr was an independent organisation whose head office was the department of the Oberkommando der Wehrmacht, specifically the OKW/WNV/FU.