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Cold War
Operatiën en Inlichtingen   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) 1 although it was also known under other names. Nevertheless, the organisation is often (wrongly) identified as Gladio, after the Italian SBO branch.

Although O&I had a good relationship with NATO and with sister organisations in other countries, like Germany, Belgium and the UK, it was the only fully autonomous and fully self-controlled stay-behind organisation in Europe. It was neither controlled by NATO, nor by any other foreign agency, including MI6 and 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), a radio transmitter and receiver (spy radio set) and sometimes a weapon and ammunition. These items 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, which consisted of a staff and field agents [1]. The staff of ± 20 people was involved with organisational tasks, administration and instruction and training of field agents. In the event of a war with the Warsaw Pact countries, the staff would be moved to a safe base in the UK, North America or Canada.

The field agents were divided into organisers and operators. An organiser was specialised in reconnaissance, forging ID papers, sabotage, information gathering, psychologic warfare, organising 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 [5].

In 1990, after stories about subversive actions by the Italian SBO 'GLADIO' had reached the press, Dutch Prime Minister Ruud Lubbers confirmed the existence of a Dutch SBO. He also stated that, unlike the other SBOs, the Dutch organisation was autonomous and was not controlled by NATO, MI6 or the CIA. Less than two years later he saw himself forced to dismantle the organisation.

  1. Although the official name for the Dutch SBO was O&I, it is sometimes referred to as I&O, even by people who worked for the organisation [5] and by government officials [10]. In 1985, the name was changed to A&B, but the old names O&I and I&O also remained in use. In the scope of this page we will use O&I.

Dutch stay-behind radio sets on this website
British Type 3 Mark II (WWII)
British Type A Mark III (WWII)
Whaddon Mk VII spy radio set (Paraset)
American spy radio set TR1 or SSTR-1 (WWII)
Short-range UHF duplex radio link (WWII)
British Mk-119 (WWII)
ZO-47 radio set developed by Philips/NSF around 1957
Watertight modular RT-3 radio set developed in the USA (also known as RS-1 and AN/GRC-109)
Modular valve-based US spy radio set (made by Motorola as the RS-6)
Modular German SP-15 spy radio set, known in the Netherlands as FSS-7 and modified with a synthesizer
Fully automatic British PRM-4150 suitcase transceiver, developed by RACAL. Known in the Netherlands as DZO-81.
Fully digital pan-European clandestine radio station FS-5000. Also known by its codename HARPOON. In the Netherlands known as AZO-90.
 Detailed description of each radio

Other equipment
High-speed burst encoder
During WWII, The Netherlands had two independent intelligences agencies, both of which operated from England under the authority of the Dutch Government in exile:

  • BI - Bureau Inlichtingen
    This was the Intelligence Bureau. It was controlled by the Dutch Government in exile (London) and was similar in nature to the British MI6. The BI was tasked with gathering military, political and economic intelligence, mainly on Dutch soil.

  • BBO - Bureau Bijzondere Opdrachten
    This was the Special Operations Bureau. It operated directly under (and was largely controlled by) the British Special Operations Executive (SOE). The BBO's task was to set up a resistance organisation and execute sabotage operations in occupied Netherlands.
Bureau Inlichtingen   BI
BI was led by Colonel Jan Marginus Somer who had already developed plans for a secret section of the Dutch General Staff just before WWII under the name GS III C. In the event of war, the main tasks of the section would be active intelligence gathering (espionage) and stay-behind. By 1939, Somer had successfully initiated GS III C, but it was too late to be of much use during the war.

Once the war was over, Somer rejuventated his GS III C section, albeit in a less ambitious form than he had anticipated. The section was actually the post-war variant of the wartime BI. For the stay-behind division of his section, he needed communication equipment. After having used a variety of Army Surplus (mainly from Belgian stores), he managed to secure a budget of NLG 20,000 (EUR 9100), for the development of the first (and only) Dutch spy radio set: the ZO-47.

The order for the development was given by Somer in 1946 to Philips/NSF. Development took most of 1947 and by the end of that year the radio was ready for its first field test. In early 1948, the first batch of 100 units was delivered to the BI. By that time, Somer had already been appointed head of intelligence in the Dutch Indies and was succeeded by J.J.L. baron van Lynden. This intelligence section (i.e. the former BI) would later become known as the I-service.

 More about Jan Marginus Somer
 More about the ZO-47 radio set

Bureau Bijzondere Opdrachten   BBO
Around the same time (1946), a former secret agent of the wartime BBO, Henk Veeneklaas, had developed his own plans for a stay-behind organisation. With the lessons learned from WWII, for example the now famous Englandspiel that had cost more than 54 lives, he was convinced that The Netherlands needed a strong and well-organised resistance in the event of another war.

When he conveyed his plans to the Dutch Royal Commander-in-Chief Prins Bernhard, the latter put him in contact with Louis Einthoven, the newly appointed head of the Dutch Bureau of National Security (BNV, later: BVD, now: AIVD).

Einthoven was easily convinced and allowed him to setup an effective operations unit which was actually the post-war varant of the wartime BBO.

The new organisation did not officially exist and became the direct responsibility of the Dutch Prime Minister. This secret operations section would later become known as the O-service.

 More about Henk Veeneklaas

Two secret organisations
During the first years, the O and I service operated independently from each other, without each of them knowing about the other's existence. The I-service was controlled by the Ministry of Defense and reported directly to the Minister. The O-service on the other hand, fell under the Ministry of General Affairs and reported only to the the Prime Minister. Around 1948, the SBOs in various European countries formed the Western Union Clandestine Committee (WUCC) in which thoughts were exchanged about the theoretical structure of a stay behind organisation.

After NATO was established in 1949, it took over the military aspects of the Western Union as well as (in 1951) the tasks of the WUCC. At NATO's headquarters – known as SHAPE – a Special Projects Branch (SPB) was established, which was tasked with Unorthodox Warfare (UW). During peace time, the so-called Clandestine Planning Committee (CPC) would form the link between the SPB and the various SBOs. The CPC would later be renamed Allied Clandestine Committee (ACC) and eventually to Allied Coordination Committee (also abbreviated to ACC).

In 1961, the first attempts were made to merge the activities of the O-service and the I-service. This plan met strong opposition from the founder and initial leader of the O-service, Henk Veeneklaas. He argued that the two services were too different to be merged. In his opinion, the I-service was a military organisation whilst the O-service was purely a civil one. In 1967, the problem was solved by discharging the heads of both services and appointing a new coordinator.

From this time onwards, the Dutch clandestine service was known as O&I (sometimes called I&O by its members), with the two services working independently, but under supervision of the coordinator. The main office of the organisation was housed in villa Maarheeze in Wassenaar (near The Hague) under the cover of the Foreign Intelligence Service (IDB). The former BI (by now the I-service) was housed here since May 1945.

The image on the right shows villa Maarheeze in later years (2014). It is currently used as a high-profile office building and can be rented.

For emergency purposes, the agents carried a so-called Green Card 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 Card. The police officer could then call a special telephone number in The Hague to verify a password that was specified on a separate card.

Front side of the 'green pass' with serial number 259, held by Herman Schoemaker [5].
Rear side of the 'green pass' with serial number 259, held by Herman Schoemaker [5].

O&I was able to carry out its duties more or less undisturbed throughout its existence. Never­theless, some of its caches (hidden storage places with weapons, money and communications equipment) were discovered over time. The following incidents reached the Dutch press:

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 1983/84 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 ever found [5].

In 2007, the Dutch Minister of Defense confirmed to the Dutch Parliament that the weapons cache had indeed been robbed but that a recent investigation had revealed that the weapons found with the criminals were of a different brand and/or model than those taken from the cache [10].

Radio equipment
From the beginning of the clandestine network, the organisation had used a wide variety of radio equipment, mainly from Dutch, US and German origin. This equipment is described in detail further down this page. While suitable for communication between agents and the government in exile, it was largely incompatible with the equipment used by SBOs in other European countries.

In the early 1980s, the Allied Clandestine Committee, or ACC — attached to NATO headquarters SHAPE in Mons (Belgium) — approved the development of a pan-European communication system for all European stay-behind organisations, including some neutral countries such as Sweden and Switzerland. The new clandestine radio station was developed by manufacturer AEG Telefunken in München (Germany) — in close cooperation with MI6 in the UK — under the codename HARPOON.

As the Dutch O&I urgently needed a replacement for the ageing FSS-7, and the new HARPOON radio sets were not expected any time soon, the RACAL PRM-4150 (TITHE) was choosen as an intermediate solution. It was already in use with the British Armed Forces, the Diplomatic Wireless Service (DWS) and stay-behind, and had a proven track record. It became known as the DZO-81; Data Zend-Ontvanger (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 adopted the single-agent concept, in which the intelligence agent (i.e. the organiser) also operated the radio.

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 was about to collapse (1991). As a result, HARPOON would be the final 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 AEG-Telefunken designator was SY-5000.

In total, The Netherlands received 110 HARPOON units between 1988 and 1990. The initial five units were received in November 1988. Two of these were used for training operators. The next shipment of 35 units was received in December 1988 [4]. The remaining 70 were received in the 2nd half of 1989 and in the 1st quarter of 1990.

In 1990, the first international Long Range (LOR) tests were carried out, and the results with the FS-5000 sets were promising. By March 1991, all sets ordered by the various countries had been delivered. As the Dutch organisation had already developed a computer system and software for secure message processing — back in 1989 — the Netherlands became the first country with a fully automated FS-5000 store-and-forward message handling system [4].

The LOR tests and the software deveopment took place at NEBAS, the Dutch base station at Villa Maarheeze in Wassenaar (near The Hague) 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 with less public exposure 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.

A en B
In 1985, after the discovery of the weapons caches near Heythuysen (1980) and Rheden (1983), the organisation was reorganised. It was decided that the caches would be cleared and would only be refilled when there actually was a clear threat of war. In the meantime, the weapons and explosives were under control of the Dutch Military Police (Koninklijke Marechaussee).

At the same time, the organisation was renamed to A en B (A and B), with A being the former O (Operations) and B being the old I-branch (Intelligence). Nevertheless, most people kept using the old name O&I. In order to avoid confusion, the tasks of the two branches were reconfirmed by (then) Prime Minister Ruud Lubbers as follows:

A-service (Operations)
B-service (Intelligence)
  • Psychological warfare
  • Mental resistance of the population
  • Sabotage
  • Intelligence gathering
    (military, political, economic)
  • Infiltration and exfiltration
    of people and goods
Despite the various incidents with caches in the 1980s, the existence of the organistion remained secret for a long time. All that changed when in 1990 the Italian SBO 'GLADIO' started appearing in the headlines. Gladio was suspected of involvement with some ultra right-wing incidents and terrorist attacks. As a result, (then) Italian Prime Minister Guilio admitted on 3 August 1990 the existence of a secret SBO – named Gladio – and revealed that it operated under NATO control.

The indicents raised international public awareness of the secret organisations, and resulted in a series of public hearings and investigations in countries like Germany, Belgium, Switzerland and The Netherlands. On 13 November 1990, Dutch Prime Minister Ruud Lubbers publicly confirmed the existence of a Dutch SBO, but emphasized that it was completely independent and was not (and had never been) under control of NATO, MI6, the CIA or any other foreign organisation.

The end
After the fall of the Berlin Wall in 1989 and the subsequent collapse of the Soviet Union (USSR) in 1991, the threat of a possible Soviet invasion was no longer deemed realistic and the necessesity for a secret stay behind organisation had more or less disappeared. Meanwhile, in 1990, the new European HARPOON radio system (AZO-90, FS-5000) had become available and The Netherlands was the first country to to have implemented a fully automated message handling system.

In 1991, it became evident that the existing premises in Wassenaar attracted too much attention. In December of that year the Dutch base station NEBAS was moved to a more convenient location at Fort de Bilt (near Utrecht). Despite all this, Prime Minister Lubbers felt he had no other option than to shut down the entire operation. In 1992, he sent a personal letter to the agents of both services in which he thanked them for their loyalty and insisted that any details remained secret.

Members of the A-service (the former 'O') also received a personal letter from Prins Bernhard who said he had warm feelings for the organisation and had followed them with great interest from 1942 until now (1992). The administrative closure took until 1994, but once that was handled, the secret Dutch SBO was history. The former members receive a small pension for their services.

Eye witness: Herman Schoemaker
Former stay-behind radio instructor, 15 December 2013

For obvious reasons, members of the network had to maintain 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 25 years ago, the network has not been declassified by the authorities yet. Nevertheless some former members have recently 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

Radio equipment
Over the years, the Dutch stay-behind organisation used a variety of radio sets, ranging from wartime valve-based British spy radio sets, to fully automatic digital long-range radio stations with built-in encryption. Below is an overview of all radio sets that are known to have been used in this context in The Netherlands. Please note that not all O&I personnel will have used all of these radios in an operational context. The use of the following sets has been confirmed.

Type 3 Mk. II   B2
The Type 3 Mark II, commonly known as the B2, is arguably the most well-known spy radio set of World War II. It was developed in 1942 and was used throughout the war by many agents that were dropped over occupied territory. It is heavy and is housed in an 'unobtrusive' travel suitcase.

After WWII, the B2 was used for several years in some European countries (e.g. the Netherlands) by the Stay-Behind Organisation (SBO) [12].

 More information

Type A Mk. III   A3
The Type A Mark III, commonly known as the A3, was much smaller than the B2, but was suitable for short to mid-range communication only. Like the B2 is was a left-over from WWII, but unlike the B2, it was much smaller.

The radio was usually installed inside a small children's evacuee suitcase, such as the ones that were issued during WWII in the UK [12].

 More information

Mark VII   Paraset
The Mark VII, commonly known as the Paraset, was developed in the UK around 1941, and was used during WWII by agents that were dropped over occupied territory. It is either housed in a metal or a wooden enclosure, and required the valves (tubes) to be removed before transport.

The Paraset was arguably one of the most dangerous radio sets produced by the British. In reception, the signal from its local oscillator was strong enough for the Germans to locate the agent by means of Radio Direction Finding (RDF).

 More information


TR-1   SSTR-1
Like the British B2, the American SSTR-1 was housed in a common unobtrusive travel suitcase. During WWII, some SSTR-1 units had been used in the Netherlands and in Belgium.

After the war, some SSTR-1 units were used by the Dutch SBO, but not to the same extent as the British B2. In the Netherlands, the SSTR-1 was known as TR-1 [12].

No further information at present.


S-Phone   wanted item
The S-Phone was a short-range full-duplex UHF radio system, developed in 1942 in the UK for use by the SOE and by resistance fighters, during droppings and landings on occupied territory.

As the radio only worked in the line-of-sight (LOS), it was relatively safe against interception. In the early years of the Dutch SBO, it was used during infiltration and exfiltration exercises [12].

 More information

Another left-over from WWII that was used by the Dutch SBO, is the British Mk.119. It was developed in late 1940 by HMGCC (now: GCHQ) at Hanslope Park (UK), and was also used by Special Forces (SF) and by the British Diplomatic Wireless Service (DWS) for communication with the British Embassies overseas.

The radio was available in two versions: a three-piece solution in which transmitter, receiver and power supply unit (PSU) were each housed in a separate container, and a single-piece variant in a wooden case, shown in the image on the right.

The B2, A2 and Mk.119 were the last wartime long-range radio sets that were used by the Dutch SBO, before moving to newly developed post-war equipment from Dutch, German and American manufacturers.

 More information

It was decided to replace the leftovers from WWII by a new spy adio set that would be developed in the Netherlands. In 1946 the order was given by Colonel J. Somer of GS III C (foreign intelligence) to Philips for a total of NLG 20,000 (EUR 9100).

Designated ZO-47, the first 100 units were delivered to O&I early in 1948, followed by the slightly improved ZO-47/01 a couple of years later. The radio is suitable for sending messages in morse code on a limited number of channels.

 More information


Sometime during the 1950s, it was decided to make the switch to foreign equipment, such as the RT-3 shown in the image on the right. De­sig­nated RS-1, the set was developed for the US Central Intelligence Agency (CIA) and is housed in three watertight containers.

As the RS-1 (RT-3) was produced for the CIA in large quantities, it was cheaper for The Nether­lands to buy this one, rather than develop its own spy radio sets.

 More information


In the early 1950s, compact spy radio sets became available from the US, such as this RS-6 that was developed in 1951 by Motorola. It was known in The Netherlands as RT-6 and was a lightweight alternative for the RT-3 (RS-1).

In 1960, O&I replaced the electromechanical vibrator of the RT-6 with an in-house developed electronic transistor-based alternative. Further­more, the American circular power connectors were replaced by 9-pin D-sub connectors.

 Dutch version of the RS-6
 Standard RS-6


FSS-7   SP-15
In the late 1960s and early 1970s, the older radio sets were gradually replaced by the Ger­man SP-15 spy radio station, which was known in The Netherlands as FSS-7. The station con­sisted of a crystal-operated transmitter, a very sensitive receiver and one or two power supply units, all stowed in a watertight green container.

In a midlife upgrade the set was enhanced with a synthesizer and an electronic burst encoder.

 Dutch version of the FSS-7
 Standard SP-15


DZO-81   PRM-4150
In 1981, O&I selected the British PRM-4150 as a gap-fill solution between the ageing FSS-7 and the forthcoming FS-5000 (HARPOON), which was expected for 1990. The PRM-4150 was already in use in other European countries for diplomatic and military communications. In The Nether­lands it was known as DZO-81.

 More information


AZO-90   FS-5000 / Harpoon

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 AEG-Telefunken designator was SY-5000.

In total, The Netherlands received 110 HARPOON units between 1988 and 1990. The initial five units were received in November 1988. Two of these were used for training operators. The next shipment of 35 units was received in December 1988 [4]. The remaining 70 were received in the 2nd half of 1989 and in the 1st quarter of 1990.

 More about the AZO-90 (FS-5000)


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 Maarheeze in Wassenaar (Netherlands), under the cover of the Foreign Intelligence Service — Inlichtendienst Buitenland (IDB).

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 Heythuysen) and 1983 (near Rheden).

  • O&I
    Operatiën en Inlichtingen (Operations and Intelligence)
  • I&O
    Inlichtingen en Operatiën (Intelligence and Operations)
  • I/O
    Alternative notation for I&O
  • O/I
    Alternative notation for O&I
  • A en B
    New name since 1985: A and B
  • A&B
    Alternative notation for 'A en B'
International trainings and exercises
    International ACC exercise, Jan 1976 (UK)
    International ACC exercise, May 1977 (UK)
    International ACC exercise, May 1988 (USA) June 1980 (Italy)
    Training program (radio)

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], but in particular from the PIVOT report by Dick Engelen [1] and the 2013 thesis of Herman Schoemaker [5] the latter of whom was a radio instructor for the organisation for many years.

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
1948   First 100 radio sets
The first radio sets are delivered early in 1948. These are probably ZO-47 manufactured by Philips/NSF.
1949   Founding of NATO.
4 April 1949.
1966   Compromise
Discovery of weapons cache in the Wieringermeerpolder.
1980   Compromise
Discovery of weapons cache in Heythuysen (Limburg).
1981   Introduction of the DZO-81 transceiver.
1983   Compromise
Discovery of weapons cache near Rheden.
1984   Weapons stolen from a cach near The Hague (Scheveningse Bosjes)
1985   O&I renamed to A&B
1989   Fully automatic radio system AZO-90 (Harpoon)
1989   Fall of the Berlin Wall
1990   Italian stay-behind, known as Gladio, uncovered
1990   Dutch stay-behind uncovered
13 November 1990. 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.
1991   Move to new location
In December 1991, the organisation is moved from Wassenaar to Fort de Bilt, near Utrecht. Here a large Log-Periodic antenna is erected.
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 by Prime Minister Ruud Lubbers. In 1994, all administrative tasks have been completed and the network is officially closed down.
Timeline of radio equipment
The diagram below shows which radio sets and burst encoders were used and (on average) when they were introduced. Only the ZO-47 was developed and built in The Netherlands, all other sets came from the USA, Germany and the UK. At the launch of the network, around 1946, leftover spy radio sets from WWII were used, such as the Type 3 Mark II (B2), Type A Mark III (A3), S-Phone, Mark VII (Paraset) and Mk 119. They were abandonned as soon as the ZO-47 became available.

Note that the RS-6+ is an upgraded version of the RS-6, in which the vibrator pack s replaced by an electronic circuit. In the same vein, the FSS7+ is an upgraded version of the FSS-7 (SP-15) in which a frequency synthesizer, developed exclusively for The Netherlands, replaced the crystals.

  1. Scholten wil praten over wapenvondst
    Newspaper article about the discovery of a weapons cache near Heythuysen (Dutch).
    Reformatorisch Dagblad. 18 June 1980.

  2. Bestaan van geheim depot toegegeven
    Newspaper article about the discovery of a weapons cache near Rheden (Dutch).
    NRC Handelsblad. 6 Oct 1983.

  3. Wapens en explosieven waren afkomstig uit geheim depot
    Newspaper article about the discovery of a weapons cache near Rheden (Dutch).
    1983. Undated.

  4. Vragen ... over wapenvondsten in de bossen tussen Velp en Rozendaal
    Parlementary questions and answers (Dutch, Second Chamber of the State General).
    1983-1984. 21 September 1983.

  5. Vragen van de Tweede Kamerleden Teven en Boekenstijn (VVD) — 2060725030
    Vragen van het Tweede Kamerlid van Velzen (SP) — 2060725260.
    Parlementary questions and answers (Dutch, Second Chamber of the State General).
    Ministerie van Algemene Zaken, 9 November 2007.
  1. H.J. Bekker, Geschiedenis van de Sectie Algemene Zaken
    History of the Section General Affairs (Dutch) (uncensored). 1
    31 December 1981.

  2. 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 (Dutch).
    The Hague, 2005. ISBN 90-5909-0489.

  3. 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. Bob G.J. de Graaff, Utrecht University. 7 June 2013.
  1. As this document contains sensitive information, we have chosen not to release it in its entirety. Redacted subsets of the document are available for download below [2][3][4].

  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 (Dutch).
    The Hague, 2005. ISBN 90-5909-0489.

  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. 1

  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. 1

  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. 1

  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. Bob G.J. de Graaff, Utrecht University. 7 June 2013.

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

  7. Wim Kramer, Mysterie in Utrecht
    RAM Magazine 136, Oktober 1992. pp. 17-19. 2

  8. Wim Kramer, Mysterie in Utrecht na jaren opgelost
    RAM Magazine 191, Oktober 1997. pp. 32-35. 2

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

  10. W. van Middelkoop, Antwoord op Kamervragen 2060725030 en 2060725260
    Answers by the the Dutch Minister of Defense to questions raised by Dutch Parliament.
    9 November 2007 (Dutch).

  11. Bart Olmer, Ex-instructeur onthult bestaan ondergrondse verzetsgroep...
    Interview with Herman Schoemaker at the event of the presentation of his Thesis [5].
    De Telegraaf (newspaper, Dutch), 9 November 2013. p. TA1.

  12. H.J. Bekker, Geschiedenis van de Sectie Algemene Zaken
    History of the Section General Affairs — uncensored version of [2].
    31 December 1981.
  1. Partly declassified and released in 2007 under the WOB — the Dutch equivalent of the FOIA.
  2. Reproduced here by kind permission from the author Wim Kramer.

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