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Gladio in The Netherlands   O&I
The Dutch stay-behind organisation during the Cold War

In the Netherlands a secret stay-behind organisation (SBO) was formed just after WWII had ended, in 1946 or 1947. For many years, this organisation was known as O&I, the abbreviation of Operatiën en Inlichtingen (Operations and Intelligence), although its name was changed a number of times. Nevertheless, the organisation is often called Gladio by the public, after its Italian counterpart.

Although O&I had good connections with NATO and with sister organisations in other countries, such as Germany, Belgium and the UK, is was the only stay-behind network in Europe that was fully autonomous and fully self-controlled. It was neither controlled by NATO, nor by any other foreign service like MI6 or the CIA [5].

Each agent had a set of manuals, coded information about agents, transmission schedules, code material, financial means (e.g. money and gold), radio transmitter and receiver (i.e. a spy radio set) and sometimes a weapon and ammunition. These were usually stored inside one or more containers that were hidden by the agent, e.g. in the attic or burried in the garden. Some of this material was also stored in other places, known as caches, both in The Netherlands and abroad.

In total, between 100 and 200 agents were involved in the Dutch network [1][5], that consisted of a staff and field agents. The staff of approx. 20 people was involved with organizational tasks, administration and instruction and training of field agents. In the event of a war with the Warsaw Pact (i.e. the Russians), the staff would be moved to a safe country like the UK or North America.

The field agents were divided in organisers and operators. An organiser was specialised in reconnaissance, forging ID papers, sabotage, information gathering, psychologic warfare, organizing illegal press, etc. In the event of a war, the organiser would autonomously built his own clandestine network. Each organiser was assigned an operator who maintained contact with the staff abroad. The operator was specialised in operating the radio equipment, coding and decoding messages, sending these messages in Morse Code and preventing interception and direction finding. Initially, the agents would operate in pairs (organiser and operator), but later, when automatic radio stations were deployed, the single-agent concept was introduced.
For emergency purposes, the agents carried a so-called Green Pass that warranted them from interference by the civil or military police. If they were discovered, e.g. by the police whilst 'on duty', they were allowed to present the Green Pass. The police officer could then call a special phone number to verify a 'password' that was mentioned on the pass.

O&I was able to carry out its duties more or less undisturbed during its lifetime. Nevertheless, some of the organisation's caches (hidden places with weapons, money and communications equipment) were discovered several times. The following incidents reached the Dutch press:
  • 1966, discovery of weapons cache in the Wieringermeerpolder.
  • 1980, discovery of weapons cache in Heijthuisen (Limburg).
  • 1983, discovery of weapons cache near Rheden.
  • 1992, discovery of weapons and communications equipment in a house in Utrecht.
There were other incidents that reached the press, such as the discovery of a large amount of weapons with Dutch criminals Sam Klepper en John Mieremet in Alkmaar (Netherlands) on 29 August 1991. According to some newspapers, these weapons were robbed from a cache in The Hague (Scheveningse Bosjes). In 1983 the robbery was discovered and reported to the police, but it was decided not to take any further action. Although it was suggested that the stay-behind network was involved in this criminal activity, no proof to support this claim was found [5].
Communications equipment
Over the years, the Dutch stay-behind organisation used a variety of radio sets, ranging from post-war valve-based spy radio sets issued by the Americans, to fully automatic digital long-range radio stations. Below is an overview of all radio sets that are known to have been used in The Netherlands. Please note that not all users will have used all of these radios in an operational context. The following radio sets were used by the Dutch stay-behind organisation O&I:
ZO-47 radio set developed by Philips/NSF around 1957 ZO-47 Watertight modular RT-3 radio set developed in the USA (also known as RS-1 abd AN/GRC-109) RT-3 Modular valve-based US spy radio set RS-6 Modular German SP-15 spy radio set, known in the Netherlands as FSS-7 and modified with a synthesizer FSS-7 Fully automatic British PRM-4150 suitcase transceiver, developed by RACAL. Known in the Netherlands as DZO-81. DZO-81 Fully digital pan-European clandestine radio station FS-5000. Also known by its codename HARPOON. In the Netherlands known as AZO-90. AZO-90

The ZO-47 was probably the first spy radio set used in The Netherlands, after the O&I organisation had been established shortly after WWII. It was developed and built by Philips/NSF around 1947. The name ZO-47 is short for Zendontvanger (transmitter/receiver) 1947.
By early 1948, about 100 ZO-47 units had been delivered to the Dutch stay-behind [5]. Messages were sent manually in Morse Code (using a morse key) via a limited number of frequencies.

The compact radio station consisted of three same-size units: a transmitter, a receiver and a power supply unit (PSU) that were connected together by means of short cables. It could easily be concealed in a watertight container, allowing the set to be stored for extended periods of time (e.g. in an attic or burried in the garden). Some sets were also stored in the so-called caches.
ZO-47/01 in the collection of the Museum Verbindingsdienst)

A cache is a secret hiding place, where large quantities of supplies (e.g. weapons, ammunition, money and radio equipment) are stored for the event of war. During the 1980s, two caches were discovered in The Netherlands, but in each case no further information about them was revealed. In 1992 however, a large cache was found in a house at at the Parkstraat in Utrecht (Netherlands). It contained weapons, explosives and also two complete ZO-47 radio stations. Due to the type and age of the discovered weapons and the radio sets, it seems that it was a 'forgotten cache' from the early years of the Dutch stay-behind organisation [8].

Despite the desire of many museums and private collectors to obtain the discovered ZO-47 radio sets, the District Attorney ordered their destruction. Fortunately, one unit was saved from demolition and was donated to the Dutch Signals Museum (Museum Verbindingsdienst) were it was put on public display. The design of the ZO-47 was improved at least once, probably in the late 1940s or the early 1950s, and the improved device was designated ZO-47/01.

 More about the ZO-47
The RT-3 was valve-based spy radio set that was developed in the US shortly after WWII, probably around 1948. It was intended for use by the CIA for foreign clandestine operations and by stay-behind organisations. It was known in the US as RS-1 (CIA) and by its army designator GRC-109.
It is not exactly clear when the RS-1 was used in The Netherlands and how many units were deployed. Furthermore it is not entirely certain that the Dutch designator for the set was indeed RT-3. According to information found at the Dutch Signals Museum (Museum Verbindings­dienst) [9], it was named after the RT-3 transmitter that is part of this highly reliable set.

The RS-1, as it was officially called in the US, consists of three modules: a transmitter (RT-3), a receiver (RR-2) and a power supply unit, each packet in a watertight aluminium container.

If the RT-3/RS-1 was indeed used in The Netherlands, it was probably used as an intermediate solution between the ZO-47 and the later RS-6 (see below). It is quite possible that the RT-3 was used in parallel with the ZO-47 and the RS-6, until all units were eventually replaced by the RS-6.

 More about the RS-1 (RT-3)
In the early 1950s, suitable alternative spy radio sets became available from countries like the US, the UK and Germany. As a result, it was no longer necessary for the Dutch to develop their own equipment and it was decided to replace the ZO-47 units by the American RS-6 radio set.
The RS-6 was developed by Motorola in the US in 1951 and was initially intended for exclusive use by the CIA. It was based on the earlier RS-1. A few years later, the Strategic Air Command (SAC) started ordering the RS-6 for use aboard aircrafts during 'special' (clandestine) missions.

From that moment on, the RS-6 became noticed by other services and was used as a clandestine radio station (spy radio set) for stay-behind organisations. In The Netherlands it was used by O&I from the mid-1950s onwards. It consisted of a transmitter, a receiver, and a power supply.

A fourth box, the so called filter unit, was used to connect the other three units together. In the early spy radio sets, an electro-mechanical vibrator was commonly used to convert battery voltages (e.g. 6V) to the much higer voltages needed for the valves (e.g. 130V). Such vibrators were not very reliable, especially when the radios were stored for extended periods of time.
In 1960, O&I asked for a solution and it was decided to replace the vibrator with an electronic transistor-based alternative. This resulted in a modified version of the RS-6, in which the so-called power inverter was built inside the filter unit. Futhermore, some units were modified by replacing the typical American circular connectors by standard 9-pin sub-D connectors.

 More about the RS-6
 More about the Dutch RS-6
FSS-7   SP-15
In the late 1960s and the early 1970s, the older radio sets were gradually replaced by the German SP-15 spy radio station. This station consisted of a crystal-operated transmitter, a very sensitive receiver and one or more power supply units. It was in use for a number of years already with the German Intellicence Agency (BND), the German Special Forces (SF) and the German stay-behind.
At the heart of the SP-15 radio station was an FS-7 valve-based transmitter, made by Pfitzner, and the fully transistorized FE-8 receiver that was made by Wandel & Goltermann. Both units were developed in Germany in the late 1950s.

In the mid-1970s, the Dutch FS-7 transmitters were modified for use in combination with a synthesizer that was developed by RACAL in the UK, especially for the Dutch organisation. From then on, the station was known as FSS-7. The image on the right shows the Dutch SP-15 setup, complete with its watertight container.

In order to minimize the risk of interception and direction finding, the radio sets were equipped with a so-called burst transmitter; a device that allowed a pre-recorded message to be play back in morse code at very high speed. Initially, the American tape-based GRA-71, which was also used with the earlier RS-6 radio stations, was used for this. They were later replaced by the fully electronic Speicher (English: memory), built by Pfitzner, and eventually by the more versatile MMP.

 More about the SP-15
 More about the Dutch FSS-7 (SP-15 with synthesizer)
DZO-81   PRM-4150
In the early 1980s, the ACC (Allied Clandestine Committee), attached to NATO headquarters SHAPE in Mons (Belgium), decided to develop a pan-European communication system for all stay-behind organisations in Europe, including non-NATO countries such as Sweden and Switzerland. It was decided that the German manufacturer AEG Telefunken would develop the new clandestine radio station, in close cooperation with MI6 in the UK, under the codename HARPOON.
As the Dutch O&I needed a replacement for the ageing FSS-7 (SP-15), and the new HARPOON radio sets were not expected until the late 1980s, the RACAL PRM-4150 was choosen as a gap-fill solution. It was already in use with the British Armed Forces, the Diplomatic Wireless Service (DWS) and stay-behind, and had a proved track record. It became known as the DZO-81; Data Zendontvanger (data transceiver) 1981.

It consisted of a transmitter, a receiver, an automatic antenna tuner and a coding device, mounted together in a Samsonite briefcase.

The DZO-81 no longer required the ability to send and receive messages in morse code, as the coding unit could automatically send and receive messages at pre-determinded time schedules. As a result, separate radio operators were no longer required and the organisation changed to a single-agent concept, where the intelligence agent (i.e. the organiser) also operated the radio.

Unfortunately, not many DZO-81 units have survived. Following the discoveries of a number of caches in the Netherlands in the 1980, the Dutch Government saw itself forced to dismantle the organisation and ordered destruction of the remaining equipment. Most of the equipment was subsequently collected and destroyed at Hoogovens (blast furnaces) in IJmuiden (Netherlands). Fortunately though, the officer responsible for the destruction kept back one of each model, and donated it to the Dutch Signals Museum (Museum Verbindingsdienst).

 More about the PRM-4150 (DZO-81)
AZO-90   FS-5000 / Harpoon
By the late 1980s, the new HARPOON system, developed by AEG Telefunken, was ready to replace all existing clandestine radio sets in Europe. By this time, the Berlin Wall had already fallen (1989) and the Soviet Union would soon collapse (1991). As a result, HARPOON would be the last set.
The official designator of the HARPOON system was FS-5000, but in the Netherlands it was known as AZO-90, short for: Automatische Zender-Ontvanger (automatic transceiver) 1990. The Telefunken designator was SY-5000.

In total, The Netherlands received 110 HARPOON units between 1988 and 1990. The first five units were received in November 1988. Two of these were used for training. In December 1988 a shipment of 35 sets was collected [4]. The remaining 70 sets were received in the 2nd half of 1989 and the first quarter of 1990.
FS-5000 with DSU inside Samsonite attaché case

In 1990, the first international Long Range tests (LOR) were held and the results with the FS-5000 were very good. By March 1991, all sets ordered by the various countries had been delivered. Back in 1989, the Dutch organisation had already developed its own computer system for secure message processing and became the first country with a fully automated FS-5000 message handling system [4].

All of this took place at NEBAS, the Dutch base station at Villa Maarheze in Wassenaar (near The Hague, Netherlands) where O&I had been located since the beginning under the cover of the Dutch Foreign Intelligence Service (Inlichtendienst Buitenland, or IDB).

In December 1991, NEBAS was moved to a more convenient location in Utrecht, where a completely new building had been erected at the premisis of the KMAR (the Royal Dutch Military Police) at Fort De Bilt. Here they were able to install a large Log-Periodic antenna.

 More about the FS-5000 (AZO-90)
Eye witness: Herman Schoemaker
Former stay-behind radio instructor, December 2013

For obvious reasons, members of the network had to obtain strict secrecy during the operational years of the organisation (1946-1992). This continued after the network was dismantled in 1992. Although this is now over 20 years ago, the network has not been declassified by the authorities yet. Nevertheless some former members have decided to break their code of silence.
An example of such a former agent is Herman Schoemaker from Soest (Netherlands). He was a radio instructor of the Dutch stay-behind and worked for the network from the early 1960s right until the end in 1992. In June 2013 he graduated at the University of Utrecht with his paper about the Dutch stay-behind O&I [5].

On the last opening day of our special exhibition Secret Communications, in Duivendrecht (near Amsterdam) in November and December 2013, we had the honour of meeting Schoemaker and listen to his more than exiting Cold War stories.

To our surprise, he was accompanied by two other former agents who were involved in the same type of work. Although one of them was an old friend of Schoemaker, he only learned about his involvement in the network when he accidently recognized his voice during a training.

Schoemaker was trained as a radio specialist and he in turn trained other agents in the use of the various radio sets. During the early days (i.e. in the early 1960s) this involved using morse code and the use of the FSS-7 (SP-15) spy radio set and its burst encoders. Especially the use of morse code, the transmission frequency schedules and the use of the cryptographic code material, required a long and intensive training, something that was greatly reduced when the automatic DZO-81 and later the fully digital AZO-90 (FS-5000, HARPOON) radio sets were introduced.

 Review of Herman Schoemaker's visit on Sunday 15 December 2013
The Dutch stay-behind organisation was commonly known as O&I, which was the abbreviation of Operatiën en Inlichtingen (Operations and Intelligence). The organisation was only known to the Prime Minister and on some occasions the Minister of Defense. It was offcially part of the General Staff of the Dutch Army and operated from Villa Maarheze in Wassenaar (Netherlands), under the cover of the Inlichtendienst Buitenland (IDB), the Foreign Intelligence Service.
Organisation I   Intelligence
At the height of the Cold War, the I-department counted some 200 people. Between 20 and 30 of them were responsible for the organisational tasks, the administration and training (the staff). In the event of a war, the staff would be moved to a safe country. The rest were the agents that would stay behind in the occupied country. The following 17 bureaus were known:
  1. Secretariaat en Transport (administration and transport)
  2. Lijnen, (escape routes from occupied Netherlands)
  3. Inlichtingen en Netwerken (intelligence and networks)
  4. Radioverbindingen (radio communication)
  5. Reproductie (reproduction)
  6. Radiotechniek (radio engineering)
  7. Inlichtenoperaties via de IDB (intelligence via Foreign Intelligence)
  8. Codezaken (coding issues)
  9. Veldveiligheid (field safety)
  10. Luchtfiltratie (infiltration and exfiltration via the air)
  11. Zeefiltratie (infiltration and exfiltration via the sea)
  12. Speciale netwerk (special network)
  13. Short-term netwerk (short-term network)
  14. Comptabiliteit (accountancy)
  15. Financiële netwerken (financial networks)
  16. Meteo netwerk (weather reports)
  17. Documentatie/falsificatie (counterfeit documents, micro-photography, etc.)
Organisation O   Operations
This part of the organisation was responsible for the operational field work, such as sabotage, raids, liquidations, etc. In case of war, the organisation had access to weapons and explosives that were stored in hidden locations, the so-called caches. Approximately 40 such caches were present in the Netherlands, but these were dismantled after discoveries in 1980 (in Heijthuisen) and 1983 (near Rheden).
Below is an attempt to create a timeline of events that are related to the Dutch stay-behind organisation. For this timeline, information is used from the sources listed below [1-6], but in particular from the PIVOT report by Dick Engelen [1] and the 2013 thesis of Herman Schoemaker [5] who was a radio instructor for the organisation.
1945   End of WWII

1946   Plans for stay-behind organisation in The Netherlands.

1947   Development of ZO-47 radio set
Philips/NSF develops the first clandestine radio sets

Early 1948   First 100 radio sets
The first radio sets are delivered. These are probably ZO-47 manufactured by Philips/NSF.

4 APR 1949   Founding of NATO.

1966   Compromise
Discovery of weapons cache in the Wieringermeerpolder.

1980   Compromise
Discovery of weapons cache in Heijthuisen (Limburg).

1981   Introduction of the DZO-81 transceiver.

1983   Compromise
Discovery of weapons cache near Rheden.

1989   Fully automatic radio system AZO-90 (Harpoon).

1989   Fall of the Berlin Wall

1990   Italian stay-behind, known as Gladio, uncovered

13 NOV 1990   Dutch stay-behind uncovered
After questions in parliament, Dutch Prime Minister Ruud Lubbers confirms the existence of a Dutch stay-behind organisation.

1991   End of Warsaw Pact
The Warsaw Pact falls apart, which is effectively the end of the Cold War.

1992   Compromise
Discovery of weapons and communications equipment in an abandonned house at the Parkstraat in Utrecht. Among the many weapons and ammunition found, were two ZO-47 radio sets.

1992   Shutdown
The Dutch stay-behind organisation O&I is officially dismantled.

  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. 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.

  3. 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.

  4. 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.

  5. Herman Schoemaker, Een geheime organisatie in beeld
    De Nederlandse stay-behind-organisatie, geheim, onafhankelijk en zelfstandig?
    The Dutch stay-behind organisation, secret, independent and autonomous? (Dutch).
    Thesis under supervision of Prof. Dr. B.G.J. de Graaff, Utrecht University. 7 June 2013.

  6. Frans Kluiters, personal correspondence.
    November-December 2008.

  7. RAM Magazine, Mysterie in Utrecht
    RAM 136, Oktober 1992.

  8. Wim Kramer, Mysterie in Utrecht na jaren opgelost
    RAM 191, Oktober 1997. pp. 32-35.

  9. Museum Verbindingsdienst (Royal Dutch Signals Museum)
    Retrieved February 2009.

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