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European Stay-Behind Organisations · SBO

After WWII, the Cold War was a state of political and military tension between the powers in the Western-Block (USA, NATO and allied countries) and the powers in the Eastern-Block (USSR and Warsaw Pact countries), starting around 1947. The virtual line between the two powers became known as the Iron Curtain [8][9].

As the countries in the West were constantly fearing an imminent attack by the East, many western countries developed a secret underground army that would stay behind in the event of an invasion by the Soviet Union and its partners.

It was thought that after a Soviet invasion, the government of the invaded country would make its way to a 'safe' country, like the UK or ultimately the USA. The Stay Behind Organisation (SBO) had the task to pass strategic information to its government in exile, setup a resistance organisation and carry out sabotage activities, as to undermine the authority and morale of the aggressor.

Many European countries had such an SBO and although it had a different name in each country, they are commonly known as Gladio by the public, after the Italian branch of the network. The Swiss SBO, for example, was called Projekt-26 or P26 whilst in The Netherlands it was first known as O&I (Operatiën en Inlichtingen: Operations and Intelligence) and later as A en B. Following the fall of the Berlin Wall in 1989 [10] and subsequently the collapse of the Soviet Union (USSR) and the Iron Curtain in 1991, the Cold War came to an end and the SBOs were gradually dismantled.

In order to maintain contact between an SBO, its government in exile, and the SBOs of the other countries, stay-behind agents used radio transceivers which were often hidden in caches, along with frequency charts, code material, money, weapons and ammunition. Such radio equipment is commonly known as spy radio sets, some of which are described in more detail on this website.

Leftovers from WWII
Whaddon Mk VII (Paraset) spy radio set
British Type 3 Mark II (WWII)
British Type A Mark III (WWII)
American suitcase spy radio set SSTR-1 (WWII)
Short-range UHF duplex radio link (WWII)
British Mk-119 (WWII)
Stay-behind radio sets on this website
Belgian post-war version of the UK Type 36/1 (MCR-1), made by MBLE (Philips)
Telefunken ESK-52 (made the French intelligence services)
Philips ZO-47, used by Dutch stay-behind from 1947 onwards
USA spy set RS-1 (a.k.a. RT-3 and AN/GRC-109)
Spy radio set built for the Austrian Abwehr
4-piece (or 2-piece) valve-based spy radio set
USA spy set RS-6
KSG-Sender (transmitter) developed by the BND in 1957
Mk. 121
Mk. 123
Automatic CIA agent radio set
Belgian RST-101 spy radio set (MBLE)
German spy set SP-15
Dutch version of the SP-15 with synthesizer
German spy set SP-20
LW/MW/SW pocket receiver
RR-49 receiver
FE-8 (BN-58) short wave receiver
BN-48 (UHU) backup receiver
BCRA transmitter
French TR-TG-2A spy radio set
Racal PRM-4150 (WANTED ITEM)
Telefunken spy set FS-5000
The Netherlands (O&I)
Austria (WSGV)
West-Germany (BRD)
Belgium (SDRA-8 and STC/Mob)
The Iron Curtain
During the Cold War, Europe was divided into two areas, separated by an ideological and physical border, known as the Iron Curtain which is shown as a thick black line
in the diagram below. To the west of this border was the free Western Block, consisting of the NATO countries
and neutral
West-European countries. To the east of the border was the communist Eastern Block
consisting of the Soviet Union (USSR) and the Soviet-controlled satellites of the Warsaw Pact.

Europe during the Cold War with the Iron Curtain at the centre. Based on original drawing from Wikipedia.

Throughout the Cold War, Yugoslavia
was a communist state, but managed to remain largely independent of the USSR, whilst Albiania initially was part of the USSR, but became independent in 1960. Germany was divided in West-Germany (BRD) and East-Germany (DDR). Berlin, the (then) former capital of Germany was divided in East- and West-Berlin — shown above as a black dot
at the heart of East-Germany (DDR) — whilst the capital of West-Germany was relocated to Bonn. After the reunification of Germany in 1990, Berlin once again became the capital of Germany.

Cooperating countries
The pan-European stay-behind network consisted of the (then) 16 NATO countries plus four European neutral countries [3]. In is uncertain whether or not Iceland – a NATO country without an army – actually participated.

NATO countries
  • Belgium
  • Denmark
  • Germany (West)
  • France
  • Greece
  • United Kingdom
  • Iceland
  • Italy
  • Canada
  • Luxemburg
  • Norway
  • Portugal
Neutral countries
  • Sweden
  • Finland
  • Switzerland
For communication between the agents and their government (in exile), but also between agents themselves, it was necessary to have radio equipment that could be used for long-distance communication. The equipment had to be small so that it could easily be hidden. In many cases the equipment was stored for many years in secret storage facilities (caches), often undergound.

In the early years, morse code (CW) was used as the main operating mode, for which operators had to take a long training. Furthermore, the operator had to have in-depth technical knowledge of antennas and the (complex) operation of the receivers and transmitters of the era. It will not come as a surprise that many operators were in fact amateurs radio operatprs (HAMs). Rumour has it that, in the 1970s, the Soviets had assembled longs lists of European radio HAMs that would be eliminated in case they (the Soviets) would invade Western Europe.

Between the start of the Cold War and the early 1980s, each European country founded its own stay-behind organisation and chose its own radio equipment. As a result, a wide variety of (in­compatible) radios, cipher systems and burst encoders was used for many years. When discussing 'spy radio sets', it is often unclear whether a radio set was used for diplomatic traffic, for special forces, for espionage or for stay-behind use. Some popular stay-behind radio sets are listed at the top of this page, but other spy radio sets may have been used for this purpose as well.

Because of the wide variety of (incompatible) radios, and the increased risk of using Amateur Radio Operators (HAMs), the Allied Clandestine Committee (ACC) that was attached to NATO headquarters SHAPE in Mons (Belgium), decided in the late 1970s to order the development of a pan-European system for communication between all stay-behind organisations in Europe.

This included several non-NATO countries [1]. It was also decided that the equipment should no longer reply on the use of morse code, but instead use cryptographically protected digital data. The equipment had to be fully automatic, so that a non-technical user could operate it.

The project was given the codename HARPOON, and in late 1980 the order was granted to AEG Telefunken in Ulm (Germany). In 1985 the highly adaptive HF radio set was ready for use and the Field Station became known as the FS-5000 [6]. The complete system was designated SY-5000.
Complete FS-5000 radio station

The system was capable of sending digitally encrypted messages over distances of more than 6000 km in under one second. In 1989 the Dutch stay-behind branch (called O&I) was the first to have fully automated radio traffic handling via their base station NEBAS [6]. By March 1991, all FS-5000 sets had been delivered to the SBOs, just before the various organisations were dismantled.

 More about the FS-5000 (Harpoon)

NATO Country SBO Remark
Austria OWSGV Österreichischer Wander-, Sport- und Geselligkeitsverein
Belgium SDRA8  
Canada -  
Denmark Absalon  
Finland ?  
France Plan Blue  
Germany TF BDJ  
Greece LOK  
Iceland ? Uncertain
Italy Gladio  
Luxemburg Stay-Behind  
Netherlands O&I Operatiën en Inlichtingen (also: I&O)
Norway ROC  
Portugal Aginter Press  
Spain Red Quantum  
Sweden AGAG  
Switzerland P26  
Türkiye Özel Harp Dairesi  
United States -  
United Kindom -  
Detailed information
Although quite some information about the SBOs of the various West European countries is available on the internet, much is still unknown. Furthermore, a lot of information in the public domain appears to be inaccurate or even incorrect. Detailed information about the countries listed below, is available on this website. For additions and corrections, please contact us.

In the Netherlands a secret stay-behind organisation was formed just after WWII had ended. For many years, this organisation was known as Operatiën en Inlichtingen (Operations and Intelligence) or O&I. Although its name was changed a number of times, the public commonly refers to it as Gladio.

O&I was operational from 1946 to 1992, when it was dismantled by the Dutch Government. During this time, the network consisted of 100 to 200 agents that were trained in a variety of skills and were able to operate a range of clandestine radio sets. According to several investigations, the Netherlands was the only country that had a completely automonous stay-behind organisation. It was not controlled by NATO, MI6 or the CIA.

 More about the Dutch stay-behind organisation O&I


After WWII, Austria was a liberated but controlled nation, occupied by the WWII Allies: the United States (USA), the Soviet Union (USSR), the United Kingdom (UK) and France, until 1955. As the Cold War had meanwhile begun, the Western Allies were afraid that Austria would be invaded by the Soviets once they themselves had left. In order to protect Austria's autonomy, its was decided to setup a secret underground stay-behind army, that could be activated in case of an escalation.

The secret stay-behind organisation became known under different names, such as Militärisches Sonderprojekt (Special Military Project), Einsatztruppe (Action Group) and Österreichischer Wander-, Sport- und Geselligkeitsverein (Austrian Association of Hiking, Sports and Society).

 More about the Austrian stay-behind organisation OeWSGV

  1. Erich Schmidt-Eenboom & Ulrich Stoll, Die Partisanen der NATO
    July 2016 (2015). ISBN: 978-3-86153-889-3.

  2. Leo A. Müller, Das Erben des Kalten Krieges
    1991. 156 pages. ISBN: 3-499-12993-0
  1. Dr. D. Engelen, De Nederlandse stay behind-organisatie in de koude oorlog 1945-1992
    Ministerie van Algemene Zaken, Ministerie van Defensie & Rijksarchiefdienst/PIVOT
    The Netherlands, National Archives, Institutional Investigation, 2005. (Dutch)

  2. Danielle Ganser, The British Secret service in Neutral Switzerland;
    An Unfinished Debate on NATO's Cold War Stay-behind Armies.
    Intelligence and National Security, Vol. 20, No. 4, December 2005, pp. 553-580.

  3. Daniele Ganser, NATO's secret Armies: Operation Gladio and Terrorism in Western Europe
    ISBN 978-071465607-6, 2005.

  4. Geschiedenis van de Sectie Algemene Zaken, Hoofdstuk VI, Consolidatie
    History of the Section General Affairs, Chapter 6, Consolidation. (Dutch)
    Describing the period May 1970 - December 1981. Dutch National Archives. Top Secret. Partly declassified and released in 2007 under the FOI Act.

  5. Geschiedenis van de Sectie Algemene Zaken, Hoofdstuk VII, Voortgang
    History of the Section General Affairs, Chapter 7, Progress. (Dutch)
    Describing the period December 1981 - May 1987. Dutch National Archives. Top Secret. Partly declassified and released in 2007 under the FOI Act.

  6. Geschiedenis van de Sectie Algemene Zaken, Hoofdstuk VIII,
    Van Stroomlijning tot Ofheffing

    History of the Section General Affairs, Chapter 8, From Streamlining to Dissolution. (Dutch) Describing the period May 1987 - January 1994. Dutch National Archives. Top Secret. Partly declassified and released in 2007 under the FOI Act.

  7. Telefunken Racoms, History
    Timeline -> 1985, SY5000 adaptive HF system to NATO special services.
    Telefunken website. Retrieved May 2009.

  8. Wikipedia, Cold War
    Retrieved January 2013.

  9. Wikipedia, Iron Curtain
    Retrieved January 2013.

  10. Wikipedia, Berlin Wall
    Retrieved January 2013.

  11. Wikipedia, Operation Gladio
    Retrieved February 2020.
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Crypto Museum. Created: Friday 02 October 2009. Last changed: Wednesday, 17 July 2024 - 14:19 CET.
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