HS7- 42, Special Operations Executive Signals History









10. BBC









19. S.O.





Before the war no system of communication for the special purpose of controlling subversive action was in existence. The German attack in the West and subsequent advance, leading to the occupation of the channel ports and control of the French Atlantic seaboard, made it clear that a reliable system of communication would have to be set up without delay.

SOE was at the time a part of Section "D" of SIS for the purpose of co-ordinating the planning of "Special Projects Forces" (See General Directive File 1/460/1).

In July 1940 as the result of a War Cabinet memorandum, which combined under the Ministry of Economic Warfare the departments formerly interested in sabotage work, SOE was given a charter to work as a separate organisation. It was laid down that the new organisation was "To co-ordinate all action, by war or subversion and sabotage" against the enemy wherever he may be, and encourage the respective nationals  if over-run to resist Axis control.

The organisation which grew up as the result of the charter was that, on the one hand in which the essential General Staff and the munitions of war were situated in our territory, while on the other hand its fighting personnel were in territory occupied by the enemy.

Reliable and rapid means of inter-communication were therefore essential to the accomplishment of the direction contained in the charter, and wireless telegraphy was the only method which would fulfil the requirement.

While it was clear that the reception and transmission of messages "behind the enemy lines" would be a clandestine measure, it was equally clear that the nature of the operation to be conducted created a signal problem radically different from the work done by SIS, who so far, had conducted all clandestine signalling.

SOE was therefore authorised to set up an independent system. (See CD/TC/1304-21-3-42, CD/5351-9-6-43, CD.5447-20-6-43. File 13 SIS/SOE Communications.)

It was foreseen that initially the greater part of the signal traffic would relate to the delivery of personnel and stores by aircraft, and that the most precise arrangements would have to be made in respect of time and place. To enable such arrangements to be made it was evident that inter-communication with WT stations overseas must be planned in respect to time, and it would result in interception of the messages by the enemy.

The task was  therefore made in which the following factors were considered:

a. The nature of SOE field operations.
b. The requirements in communication.
c. The enemy interception and cryptographic service
d. The enemy wireless position finding service.

From the conclusion of this appreciation the SOE Communication Plan was prepared. The chief points were:

1. The building up on "the air" of a transmission umbrella under cover of which the growth of bind the lines stations would be obscured.
2. The employment of high grade ciphers.
3. No lateral WT communications behind the lines.
4. The conduct of outward transmissions in such a manner as to render the location of the addressee impossible to obtain.

Training programmes, technical preparation, signal planning and WT station operation were all directed to the implementation of the plan.

Early January 1942 the overseas and home General Staff Missions and Country Sections were able to outline their signal requirements. These called for WT networks, ranging from the clandestine to the para-military in type, based on main stations sited in the European, Eastern and African theatres of war.

To meet the requirements is was imperative to adopt a bold constructive policy in the signals organisation, since in the geographical extent the overall network was larger than that of the Services and the provision and training of personnel of some 25 nationalities, a difficult matter. The field equipment used by the Services was not suitable for our purpose, so arrangements had to be made for the design and manufacture of field sets. As the war progressed, base stations with definite geographical commitments were erected in the various theatres as required, and during the progress of the campaigns approximately 5000 signals personnel were involved.

The sites chosen were:

GRENDON & POUNDON B: To cover N.W. Europe and Central Europe with links to Algiers, Gibraltar and Portugal.

POUNDON C: To be erected and staffed by the Americans to cover Scandinavian and other zones when necessary.

ALGIERS: To cover Spain, Portugal, Italy, Sicily, Sardinia, Corsica and a section of Southern France if necessary.
               (At a later date Tunisia)

GIBRALTAR: Emergency Station to cover Spain, Portugal and North Africa in the event of an Axis move into Spain and
                   provide links with Algiers and the UK.

MALTA: Emergency link between Yugoslavia, Cairo and the UK.

CAIRO: To cover the Balkan States, the Near East and the Arab World, with links to the UK, Algiers and Turkey.

FREETOWN & LAGOS: Emergency stations to cover a possible Axis move into W. Africa.

DURBAN: To cover Madagascar with a link to Cairo.

INDIA (Calcutta): To cover Burma, Siam, and French Indo China with links to Chungking, Kurming, Meerut, Poona,
                          Madras and Colombo.

CEYLON: To cover Malaya, Dutch East Indies, Andaman Islands, Nicobar, Mergui Archipelago. With links to London,
              Madras and Trincomalee.

AUSTRALIA (Darwin): To cover New Guinea, Borneo, Pacific Isles (Catherines and Gilberts). With links to Colombo,
                                Melbourne and Perth.

In addition to this vast Signal Network, extensive use was made of commercial and service systems - notably Cables and Wireless Ltd. - for inter-communication between SOE HQ London and subordinate HQ's overseas.

The resources of the BBC were also utilised in conjunction with the SOE networks for the transmission of messages.

In July 1942 the initial stages were in operation, but the final build up as shown in Appendix A was not in full operation until late 1943/early 1944.

For purposes of this History each sector will be described as fully as possible in the order in which they were built up, quoting references to correspondence where available.

In January 1942 an independent SOE Signals network was started under the control of its C.S.O who was responsible for co-ordinating all Signals work, and act as adviser to C.D. on all Signals matters. (See C.S.O. Charter, and M/XX168/MG File M/Gen/11).
To assist him, a GII, GIII and a Technical Officer were appointed to fulfil the respective duties laid down in the table of responsibility shown below:

C.S.O's Staff:


(GII): Signal Plans for Missions & Sections, Operational Plans Frequencies.


a. Officers: Selection and Interviews. Contact with the three Services. Promotion and Reports. Contact W.D/Pers.

b. O.R's: Personnel for Signal Units at home and abroad. Contacts D/A and D/A.1. R.Signals Records. Documents,
              interviews and tests.

c. Women Operators: Selection, Interviews & general contact with sources of supply.

G.III: Equipment (1-4).

1. Supply of equipment for Stn, X, Mission Stations, Agents' sets. Contact with D/Y.

2. Manufacturing programmes & progress reports.

3. Supply of equipment to Schools.

4. Record of all equipment with Missions & Sections, its distribution & reports on efficiency.

5. Liaison for field trials with Stn.9, STS 52 & Stn.X.

6. Records for Technical Officer.

7. Transport & Despatch.

8. Works & Buildings.

9. Telephone & Teleprinter circuits for Signals Communications.

Technical Officer:

1. Contact with Sta.9. a) On development policy  of all aparatus. b) On progress of productionin Stn.9 & with all

2. Initiation of development of Radio & Allied apparatus.

3. Representation of CSO with T.R.E. S.E.E. & Signal School, Post Office, D.S.I.R. Visits.

4. Signal Security Plans.

5. Camouflage of apparatus.

6. Field trials & operational trials.

7. Contact with Missions & Sections on suitability of apparatus, and suggested improvement.

Training: Syllabus & progress report.

Control of Staff: and accommodation.

As already mentioned in the introduction, the training of WT operators was already being done by SOE, GRENDON HALL being used for this purpose.

After exhaustive tests as to suitability of site, it was decided to build a War Station at Grendon, and establish an agents' training school at Thame Park. Forward planning also considered for the erection of a second station at Poundon, if and when traffic increased to such an extent that it could not be carried by one station. (See Introduction). Grendon was designed to cover the whole of N.W. Europe, some missions in Central Europe and the Scandinavian States. The work on the War Station was given the highest priority possible and a target date for completion fixed for early May 1942.

The work involved was considerable, when it is taken into consideration that the site must of necessity be:

a. Isolated to contribute largely to its security (which for purposes of secret signalling is vital).
b. Free from "electrical" interference.
c. Within easy reach of it's HQ.
d. In an area where telephone and teleprinter lines could be made available.
e. Having sufficient land area on which to erect two lots of buildings, (one lot for receiving and one lot for transmitting),
    situated at a suitable distance apart so that the outgoing signals would not interfere with the incoming signals.

The latter had to be especially borne in mind because of the power used. (Base Station maximum of 250 watts as against a maximum of 20 watts for the transmitter used in the field, which would produce a much weaker signal under varying conditions  if the frequency allocation (which in turn is dependent upon frequencies allowed by the WT board) was not accurate.

The receiver site was located at Grendon, and the transmitter sited at Charndon, about 3½ miles away. The two sites being coupled together with two remote control cables, routed differently, thereby providing one main control and one alternative or emergency control link. (see maps)

Station control is usually done at the receiver end and houses the various departments which go to make up a signal station, such as: the wireless room, message distribution, teleprinters, ciphers and internal and external control.

At the station at Grendon was to be a self-contained (as indeed, is the case for all SOE War Stations), additional accommodation had to be built with provision for stores, feeding arrangements and recreational facilities. Huts being built for this purpose, in addition to the Hall itself.

Whilst this work was going on, some testing with the "field" was done, and outstations then worked by SIS "Monitored" in readiness for the eventual take-over by SOE. In all about 20 plans. The outstations were hears to advantage, traffic intercepted and passed on for comparison.

In June 1942 the station at Grendon was completed, 12 channels (
12 ontvangers en 12 zenders) being considered sufficient to meet the commitment at any time. With a receiving and transmitting aerial array to cover a wide span stretching from Spain to the Artic circle. Operations commenced.

The outcome of having an independent SOE signal system enabled the Country Sections to build up their ground organisation more speedily. This meant an increasing demand for extra circuits, and in November 1942 the site at Poundon was started.

The development of this site was done on similar lines to the one at Grendon, and by May 1943 a 40 channel station was completed at Poundon to cover Belgium, Holland, Denmark and Southern Norway.

At the same time, Grendon had been remodelled to cover France, Spain, North Africa and Northern Norway and had developed from a 12 channel station to a 32 channel station.

To man these stations successfully, Training Schools were also started for the purpose of training Base Station operators. This was initially done at Chicheley and started about April 1942, and moved to Fawley Court in June 1942, with a sub-group at Dunbar. (Training will be explained fully at a later stage).

The Signals set-up at this time was then placed under the control of an O. I/C Signals, who controlled operations and training on site, being responsible to C.S.O. London HQ for the smooth running of the Signal work.

The organisation diagram shown below will illustrate the signals control at the time:


                                                                          C.S.O. London

                                                                  Signals O. I/C Poundon HQ

                          O.C Grendon, Signal Planning, O.C. Poundon, O.C. Thame Park, O.C. Fawley Court.

This arrangement proved unsatisfactory, mainly due to the contact between Country Sections and signal Operations ans planning being poor.