Field artillery and indirect fire is totally dependent of effective and efficient communications

BACKGROUND

Between the two world wars the British Army decided that wireless communications were essential to support their doctrine, and that forward of divisional HQ wireless would be the primary means of communication.  Unfortunately this aspiration proved unachievable in 1939.  Some elements of the British Army entered World War 2 (WW2) with an ambivalent attitude to wireless.  The infantry saw little need, taking the view that face to face meetings, a loud voice and 'runners' would suffice, and addressing the problem of greater dispersion by reducing from 'square' companies and platoons to 'triangular' ones (ie 3 sub-units instead of 4) to keep these commands manageable.  The Royal Corps of Signals (R Signals) had been formed in 1920 from the Signals Service of the Royal Engineers but starved of resources, and the division of some communications responsibilities had been insufficiently validated.

However, two parts of the pre-war British Army fully recognised the power of wireless communications: the Royal Artillery and the Royal Tank Corps.  To the tank corps they were critical, communications within and between sub-units and tanks had to have them, without them an armoured force could not be controlled.

WW1 had clearly demonstrated the limits of artillery without mobile communications, although wireless had been used to control fire on various occasions throughout the war, including by aircraft from early 1915.  In the mid 1920's an artillery officer, Lt Col Alan Brooke (later Field Marshal and Chief of the Imperial General Staff for most of WW2), had written about what could be called the 'revolution in artillery affairs' that would flow from battlefield wireless.  At about this time a manpack radio was first demonstrated and used to control artillery fire.  It was the key to indirect artillery fire on the mobile battlefield by providing communications between observers and their guns and enabling the large concentrations of mobile firepower that became a characteristics of British artillery.  

TYPES OF COMMUNICATION

Radio, or wireless as it was called in WW2, was only one of four main communications 'technologies' in use at the outbreak of WW2, all were used by artillery.  These were:

• Wireless;
• Line;
• Visual signaling, and
• Messengers.

The last was most familiar in the form of despatch riders, who were R Signals.  Above unit (eg artillery regiment) level they formed part of the Signals Dispatch Service (SDS) that used many modes of transport.  Within units many officers had an 'orderly' who delivered messages and such men were called 'runners' in the infantry. Orderlies in artillery regiments had motor-cycles.  Despatch riders were tradesmen and hence paid more than the non-tradesman orderly.  

Visual signaling used semaphore flags, marker panels (ground to air), heliographs or signaling (Aldis) lamps.  Although it was extensively taught pre-war its use rapidly died out as the war progressed after being used effectively in the East African campaign in 1940, apart from some very specialised uses. However, a specialised form of visual signaling, marker panels, was used from ground to air.  Unlike some continental armies the British made only limited use of coloured flares and the pigeon service was not used by field artillery, although the Australian artillery did deploy with pigeons on at least one occasion in the SW Pacific!

Wireless and line communications were either voice or telegraph.  On wireless voice was called 'R/T' (radio telephony) and telegraph was 'W/T' (wireless telegraphy), line telegraphy was sometimes called 'L/T'.  There was a third mode, teleprinter (teletype-writer in the US) a form of telegraph, but this was not generally used for dedicated artillery communications at any level in the British Army.

Morse code was used for telegraph, lamp and heliograph signaling, and in 'continuous wave' (CW) mode on normal HF radios in units.  However, this was not just simple Morse code, in addition to the alphabet and numbers there were codes for some special characters such as "/".  There was also a large set of two and three letter brevity codes for all manner of military expressions.  The Artillery Code that had been initially developed in WW1 covered artillery specific matters including Fire Discipline.

The British Army officially recognised three types of communications traffic:

• Conversations
• 'Unregistered Messages'
• 'Formal Messages', called 'phonograms' when sent by R/T or over line using voice.

For field artillery there was a special type of Unregistered Message - 'Fire Orders'.  This used a vocabulary of terms with special meanings in accordance with 'Fire Discipline' - the language of fire control, see the Fire Discipline page for more details.  The purpose of this was to ensure that fire control orders and reports were unambiguous and brief.  Knowing Fire Discipline for R/T and W/T was the essential expertise for artillery signalers.  

More generally all three types of communication traffic were transmitted in accordance with 'Voice Procedure' or 'Telegraph Procedure'.  Voice Procedure was introduced as radio use increased, it grew from a handful of prowords in 1940 to extensive procedures by the end of the war.  It included call signs, the phonetic alphabet, standard words and phrases and their meanings (eg 'Roger', 'Wilco', 'Over', 'Out', 'Say Again', and many more), procedures for establishing and operating communications (including such things as relaying messages), standard code names, and low level ciphers for protecting the content of messages.  

Fire Orders followed the rules of Voice or Telegraph Procedures but with some key differences.  All messages were automatically repeated back by the recipient to the sender, and if incorrect the sender repeated their message prefixed by the proword 'Wrong'.  This was a critical element in the system of preventing mistakes and associated with it was the practice that fire orders were always written down by both sender and recipient, but usually destroyed within a day or so.  Numbers were spoken without the proword 'Figures' and 'owe' was used instead of 'zero' (to avoid confusion with zero lines).  Observation Posts (OP) could call gun troops by their troop name - eg 'Able Troop', 'Easy Troop', etc, - on a battery or troop radio net.  Call signs were dropped altogether for troop and battery targets after the initial call, unless 'rotation' procedures were being used (one or two OPs engaging different targets on the same net at the same time).  The term 'net' wasn't officially used, 'wireless group' was the official term, but 'net' became vernacular probably from the 'netting call' procedure used to establish communications in a 'wireless group'.

ORGANISATION

Signalers in the British Army were divided between 'regimental signalers' in the units of all arms and services and R Signals.  Both increased throughout the war to cope with the increase in radios but the regimental signalers increased more.

In field artillery regiments R Signals provide the regimental signals section at regimental HQ.  This section provided communications forward to the gun batteries and rearwards to divisional, corps or AGRA HQ.  RA regimental signalers had comparable line and radio responsibilities within the gun batteries.

No 2 Company (squadron in armoured divisions) of each Divisional Signal Regiment provided the signal sections (troops in armoured divisions) for the divisional artillery.  These sections operated radios, laid and maintained line, provided despatch riders and operated the regimental signals office.  Sections were lettered as follows:

• H Section - HQRA, and detachments for anti-tank and anti-aircraft units.  
• E, F & G Sections - field regiments.

R Signals in division and corps HQs provided common-use line communications, exchanges and dispatch services, although a dedicated artillery telephone exchange was often established at division and corps HQs.

The other two companies, with their lettered sections, of a Divisional Signal Regiment provided communications at the HQ (No 1 Coy) and forward to brigades and non-artillery divisional units (No 3 Coy).  Similar arrangements applied in Corps and Army Signals Regiments, albeit with No 3 Coy providing artillery regimental sections.

Initially AGRAs had a signal section, basically an H section.  Eventually this became a company and responsible for the regimental signal sections in the AGRA's regiments and other elements necessary for an independently deployed HQ.  Independent sections for artillery regiments in neither divisions nor AGRAs were also established.  All types of HQRA included RA regimental signalers and driver-operators in addition to R Signals operators.

R Signals had a complex structure of signaling trades that tended to differentiate between voice and telegraph operators, and of course those in artillery sections had to be trained in fire orders.  In artillery, signalers were not tradesmen and were trained in accordance with the army standard for regimental signalers (in 1938 the syllabus covered wireless, telegraph, line and visual signaling) with the addition of fire orders.  However, this was a progressive training regime in which a soldier learnt more each year.  The consequence was that in the first years of the war a unit's organisation reflected differing levels of individual training.  As the war progressed RA 'signalers' became more generic and in about the middle of the war a tradesman was introduced, the driver-operator.  

W/T, involving Morse, was a major training load and a particular challenge for the infantry due to their casualty rates.  Signalers also had extensive training in the more technical aspects of their equipment, they needed this knowledge to operate them.  'User friendly' was not a term that could be applied to British wireless sets of the period, the technology was simple and unsophisticated, but required skilled operators.  Being able to speak with a high pitched voice was also a useful attribute.

LINE

The attraction of line was that it offered security, a lesson the British had learnt from WW1.  Intercept of German wireless traffic in 1914 had led to a rapid British victory in West Africa and the compromise of their own plans through telephone intercept by the Germans, most notably at the Somme in 1916, was an influential experience.  WW1 telephone intercept was possible because British field telephones used a single wire cable with the ground itself as a return, and British and German positions were close to each other on the Western Front.  This proximity was never a problem in WW2 and single core ('assault') cables had a weight advantage.  However, most cable was twin core.

The problem with line was that it took time to lay and was susceptible to battle damage.  In WW1 it had been British practice to bury cables 6 feet deep to protect them from German 15-cm howitzer fire.  In WW2 most cables were laid on the surface and most damage, about 70%, was from own troops, although when enemy artillery was active it caused many cable breaks.  However, as operations became increasingly mobile cable laying could not always keep up so units and formations relied increasingly on radio.  The intercept threat to cables was well recognised and lines were patrolled to detect listening devices and in the forward areas line was treated as an insecure communications medium.

Units generally had 20-line switchboards, with 40-line ones used at smaller HQs and 200-line ones at major HQs.  Artillery regiments had a large number of cable laying vehicles operated by their signals section and regimental signalers in the batteries.  The regimental section carried 15 miles of cable, and whenever possible the cable as recoverd if the regiment moved.

Line layouts were usually planned to provide redundant circuits from battery CP level and above by means of lateral links.  Each battery would connect to its flanking batteries as well as RHQ and each RHQ would link to its flank RHQs as well as HQRA.  There was no fixed configuration for the line network for a battery, regiment or divisional artillery, and the basic link layout could be either a 'ring' or a 'star' at any level.  Figure 1 shows some of the options.

Figure 1 - Line Layouts

 Normally fire orders were transmitted by voice on line, but L/T could be used in exceptional conditions.

WIRELESS

In the mid 1930's a numbering system was introduced to identify the radio types.  The last digit indicated a radio's purpose.  This was generally adhered to, the types were:

1 - short range brigade sets and artillery
2 - short range divisional sets
3 - medium range sets
4 - intercommunication sets
5 - long range sets
6 & 7 - special purpose sets
8 - infantry and manpack sets
9 - armoured fighting vehicle sets, which could be operated on the move.
0 - UHF sets

At the beginning of WW2 a British infantry division had about 75 radios, by 1944 it was almost 1000.  51 of the 75 radios were in the division's three field regiments, 42 of them operated by regimental signalers.  The number of radios in an artillery regiment approximately doubled in the course of the war.

At the beginning of WW2 the main radios were the Nos 9 and 11 sets, with very small quantities of other types for communications above brigade.  The No 9 had been designed for armoured vehicles, but was too big to fit into the available space in light and infantry tanks.  The No 11 was originally supposed to provide brigade and artillery communications, but a high power version was used in tanks without space for the No 9.  Another set, No 8, had been designed for use in infantry battalions but proved to be unsuitable for mass production.  Production of Nos 9 and 11 stopped in 1942, although the No 11 remained in artillery use throughout the war in the counter bombardment and survey units, including radio link sound ranging.

New radios were introduced, the main ones were:

No 18, was derived from the No 8 set.  It was a manpack radio designed for use in infantry battalions between companies and battalion HQ.  It was issued to artillery observers (and others) for communication with infantry.  Canada produced it as the No 58 and Australia as the No 108, a US built version, No 48, was used mainly in Burma and Italy.  No 68 was a modified version for longer range use.

No 19, replaced the No 9 set as the standard radio in armoured vehicles, including armoured OP carriers, it could operate on the move.  However, it was also used for many other purposes (it could be fitted with an amplifier to produce a high power set used in HQ armoured command vehicles) and sometimes fitted to Air OP and other aircraft.  Australia produced it as the No 109 set.  In its full configuration it was actually two radios, one HF (A set) and the other UHF (B set) used for short range inter-tank communications.  In W/T mode it provided both continuous wave (CW - Morse) and modulated CW that enabled Morse to be sent to a radio operating in R/T mode.  It could have a handset remoted by cable to about half a mile away. HF range could be up to about 20 miles with a suitable antenna.

No 21 was supposed to replace the No 11.  It was short range and although it was introduced into artillery units and had considerable use in the middle years of the war its range was too short for artillery purposes and was replaced by No 22 or No 19 where armoured vehicles replaced wheels.  

No 22  replaced most No 11 and was used for many other purposes.  It could be vehicle mounted or dismounted into a trench or building and was portable as a 3 man load.  It had remote control facilities that enabled the operator to be connected by cable to the radio up to half a mile away or to connect the radio to a line switchboard.  It could also be directly connected to another radio, using a short multi-core cable, for re-broadcast operating (ie one radio received a message and it was simultaneously re-transmitted by the second radio, this worked in both directions).  It provided both CW and modulated CW as well as voice.  The Australian built version was No 122.  Range could be up to about 40 miles with a suitable antenna.  The following Figure 2 shows the components of the complete wireless station.

Figure 2 - Wireless Set Number 22 - Complete Station

No 38, a short range manpack radio only operating in R/T mode and used mainly within infantry companies and by artillery FOs.  Each OP party received one in 1943 for FOO use, tank OPs used them to communicate with infantry.  The Australian built version was No 128 but had a different frequency range.

No 46 was a special crystal controlled and water-proofed radio for use in amphibious landings, some artillery observers probably used it.

No 62 appeared at the end of the war to replace No 22.  It was a 2 man load and notable for having its front panel labeled in both English and Russian and remained in service until the mid 1960's.

The final radio relevant to field artillery was the TR 1143, a VHF set used at batteries and artillery HQs to communicate with Arty/R aircraft once this ground-air communication responsibility was transferred from RAF to Army.  It could be connected to a HF radio for re-broadcasting.

Table 1 - Types and Characteristics of Radios

British development of general purpose VHF radio was unsuccessful because they selected an unsuitable frequency band and abandoned development thereafter.  However, VHF sets were used in AA units and the ground to air links, where the TR 1143 was used to arty/R aircraft.  Some use was made of a UK built version of the US SCR 300 called No 31.

The range of a wireless depends on several factors, notably power output, frequency,  the type of antenna and its tuning.  Lower frequencies give better range than higher ones for ground to ground use.  This means that other things being equal HF radios give greater range than VHF because VHF is limited for non-line of sight communications.  British use of HF may have been an important enabler for concentrating artillery fire because CCRA/CRA/CAGRA Representatives were probably able to communicate from the front directly to the higher HQs.  This avoided the need for re-broadcast or relay stations that would have been essential if VHF was used.

HF ranges are indicative, actual range depended on the type of terrain, time of day and antenna.  Range was usually greater during daylight.  Radios had a choice of antennas that could give greater range, although often only small antennas could be used on the move.  For example the No 22 had a 34-foot rod and 140-foot wire antennas, while No 18 had a 10- foot and a ground antenna that aided concealment but reduced range.  HQs also had several R107 HF receivers, these could be used to listen to nets in subordinate units and formations as well as monitoring 'guard' frequencies.

Figure 3 gives an indication of the complexity of higher level wireless nets.  It shows the divisional level links of 2 NZ Division, comprising 4 brigades, on 9 April 1945.  The CRA's command included 8 field and 2 medium regiments.  The division was one of the 4 divisions in 5 Corps, whose artillery included 2 AGRAs and 2 AOP sqns.  HQRA was accommodated in an armoured command vehicle (ACV), as was the division's operations staff, although in British formations ACVs were only on the establishment of armoured divisions.  In the diagram HQ 5 Corps is shown in barest outline.

Figure 3 - 2 NZ Divisional Wireless Links

Frequencies

The HF band posed problems, R/T communications were often very difficulty at night due to fading, particularly in tropical conditions, and some frequencies were always better than others.  Allocating frequencies so that all units had at least one 'good' frequency was never easy.  

The increasing number of radio nets meant that frequency allocation became a major problem as the war progressed because there were not enough.  Restricting most HF radios to rod antennas limited their range so enabling frequencies to be shared by geographically separated formations.  Nevertheless frequency allocation was a major problem when lots of formations were in a small area, such as the Normandy bridgehead, and then line was preferred.  On the other hand using the HF band minimised interference from US and German communications because they made much more use of VHF frequencies.  

Typically a formation would be given a set of frequencies for a period of perhaps a month, it would then allocate these to its units, who would allocate them internally.  The formation allocation was designed to minimise interference with neighbouring formations.  An added problem was units, such as regiments from an AGRA, joining a formation and they tended to get bad frequencies, at least until the next monthly allocation.

Unlike the US and Germany, UK did not assign specific frequency bands to particular types of unit.  Most British HF radios had overlapping frequencies, in the case of Nos 19 and 22 an identical frequency range.  This provided useful communications flexibility.  Towards the end off the war HF frequency separation was reduced from 5-kHz to 4-kHz.  Since VHF used 50-kHz frequency separation the number of available frequencies wasn't greatly different.  

British policy was to change frequencies regularly, theoretically daily, all at the same time and at the same time that stations changed their code-sign.  Of course during a month these changed frequencies were just a shuffling of the division's allocation, and sometimes just a shuffling of frequencies within a unit.  However, re-establishing a radio net after a frequency change could be a time consuming process and frequencies often remained unchanged during major operations.  One solution to the difficulties of frequency changing and generally keeping HF radios tuned to their frequency was to use fixed frequency crystals.  The problem then became distributing crystals.  However, later in the war some sets were modified for exchangeable crystals and some formations had the facilities to grind crystals to frequency.

Re-broadcasting was increasingly used and enabled a forward observer with a short range manpack radio to speak to batteries that would otherwise be out of wireless range.  In essence the manpack wireless communicated with another wireless that was directly connected to a third in the same vehicle and able to communicate over longer distances.  Alternatively the manpack set operator could speak to the operator at another station who verbally relayed the message on the same frequency.  From 1943 rebroadcast was also used for ground-air communications with Arty/R aircraft, a No 22 set being connected to a VHF set at division and corps HQRAs.  Relay and rebroadcast are illustrated in Figure 4.

Figure 4 - Re-Broadcast and Relay

Power Supply

Power supply was a major problem.  Dry (or 'battle') batteries were available for manpack radios but had a very short life, perhaps 12 hours, exacerbated by limited shelf-live that was quickly absorbed in the supply line to a distant theatre such as Burma.  This meant that secondary batteries (also called accumulators or wet cells) were the primary source of power, including for the short range manpack radios when they were not being used 'on the move'.  They were heavy and battery charging was an administrative challenge.  

Apart from tanks, vehicles did not have systems to enable radio battery charging from vehicle engines.  On tanks the vehicle and radio used the same secondary battery, based on the assumption that tanks would move enough to keep the battery charged, this proved wrong.  The original policy was central charging in each unit under the supervision of a qualified technician to maximise battery life.  However, this was seldom a practical proposition on the battlefield, exacerbated by insufficient time to charge batteries in this way.  Eventually, in 1944, 300-watt charging engines were issued to all radio stations and used by the operators while sub-units got 1260-watt engines for use by technicians.  Unfortunately 300-watt engines had a life of only about 1000 hours, not to mention being noisy - an unpopular feature in forward areas!

Maintenance

Radios were repaired by either R Signals or the Royal Electrical and Mechanical Engineers after this corps was formed in 1942.

A problem was that radios wore out.  Their performance became very poor and a challenge to even the most skilled operators.  Worn radios could be re-calibrated in workshops but reverted to their pre-calibrated state in a day or so.  Experience in Burma suggested that radios needed to be rebuilt with many new components after about 6 - 9 months of use.

PROCEDURES

At the beginning of the war 'general purpose' wireless procedures were under-developed and very few officers (or anyone else apart from signalers) were trained to use wireless.  In fact up to 1939 almost all orders were issued in writing and the role of R Signals was to deliver these written messages (whether unregistered or formal) by radio, line or despatch rider.  This use of written orders was entirely consistent with the highly planned mode of operations that characterised the British Army.

The campaign in 1940 gave a wholly false picture.  Security concerns during the 'phoney war' meant that line was comprehensively laid and little use made of wireless by the BEF.  Its effect was that wireless expertise and confidence did not develop as quickly as it should have.  Army wide there was an immense training problem, but rapid progress was made in artillery units because their commanders were very dependent on effective regimental communications.  Throughout the war the big problem was the non-motorised infantry, where wireless skills did not have a high priority and high casualty rates prevented expertise accumulating.  The inclusion of R/T procedures in the standard syllabus exacerbated the training challenge because courses had to be much longer than needed to teach equipment operating and voice procedures.

Artillery was fortunate because fire orders procedures had developed with line communications and there were well established arrangements for ensuring compliance with them, whether they were voice or telegraph.  However, while R Signals had detailed procedures the more general 'all-arms voice procedure' was not adequately established before WW2.  It evolved rapidly, often around armoured or infantry formation practices, and army wide procedures were introduced in 1942.  

In 1941 a captured German document revealed significant weaknesses in communications security and this led to major changes and standardisation, starting in late 1941 in North Africa and subsequently in all theatres.  The main problem areas were:

• Radio 'call-signs',
• Code names,
• Cipher procedures, and
• R/T procedures.  

Call-signs

Before and in the early years of the war the call-sign system was extremely poor from a security perspective. In 1942 the Army adopted 'link-signs' although the Navy and Air Force retained call-signs; two letter call-signs, using marker panels, were used to help aircraft find HQs.

At the beginning of the war the system for line use was based on 'office call-signs' that uniquely identified every formation HQ, unit and battery in the British Army.  These were letter call-signs (spoken using the phonetic alphabet), for example 'FAKG' gave 107 Field Regiment because 'F' meant Field Artillery Regiment and 'AKG' the letters for the digits '107'.  There were different letters for RHA and medium regiments and for RHA, field and medium batteries.  Part of the problem was that wireless had been envisaged as a 'one to one' communications channel, like telephone, but quickly evolved into a system of radio 'nets' using a common frequency as the number of radios increased.

For wireless use daily changing three letter 'code-signs' were assigned to HQs, units and some sub-units.  Within units and sub-units with their own code-sign a numeric suffix was added for each wireless station.  To further help the enemy each station identified itself whenever it made a call.  These three letter 'code-signs' were also used in the 'body' of messages to identify units!

The major change in 1942 was adoption of 'link-signs' (basically the German system) where the 'control station' on a wireless net did not have its own call-sign but always used the call-sign of the station it was calling or was calling it.  This was based on the premise that most traffic was between the control station and its outstations.  If outstations communicated with each other then they used their link-signs and a standard phrase for the purpose.  

These three letter 'code-signs' ('link-signs') were changed daily at midnight, along with frequencies.  Within units and sub-units with a single code-sign radio stations' 'link-signs' comprised the code-sign and a numeric suffix, and there was an additional level using a letter suffix.  For example infantry 'code-signs' went no lower than battalion, so A coy had the suffix 1, and its platoons A, B and C, so the full 'link-sign' for the third platoon of D coy in a battalion with 'code-sign' XBW would be XBW4C and abbreviated to X4C.

In field artillery each regiment and battery had a daily changing 'code-sign' for their 'link-sign', and within batteries station 'link-signs' used standard numeric suffixes as shown in Figure 5, excluding the troop leaders, with the typically used radios (Nos 19 and 22).  

Figure 5 - Field Artillery Link-signs

 On the battery net illustrated the 'link-signs' would be abbreviated and spoken as 'George 1', 'George 3', etc.

However, shortage of 'good' frequencies led many units to use a single 'regimental' wireless net instead of both battery and regimental ones.  The problem was that there were no official link-signs for this so regiments created their own.  At the end of the war official  link-signs were introduced for regimental nets embracing all batteries, they were numeric.

Codes and Ciphers

Codes were used for abbreviation and ciphers to protect the content of all types of messages except fire orders, which were always sent in clear.  Brevity codes were extensively used, most notably with W/T and L/T, and the 'Artillery Code' was an example. The daily changing code-signs for units provided some security against enemy interception. Of course sensitive messages could always be sent by despatch riders if there was sufficient time, as was normally the case for orders for major operations including their fireplans.  The general rule was that if information would be of value to an enemy intelligence officer then it was not to be transmitted 'in clear'.  The main security problem was voice traffic, particularly conversational mode that was most unsuited to ciphering.

Divisional and higher HQs had cipher sections and there could be cipher trained personnel down to unit level, although this was not usual in artillery units.  Both book and machine ciphers were used, and there were scrambler telephones (secraphones) down to divisional HQ.  Below this there were paper based 'low level' ciphers that had to balance ease of use with adequate protection.  The problem with ciphers was the distribution of keys and the ever present threat of keys being compromised.

There was, of course, extensive use of Code Words (also called Code Names or Key Words).  Basically there were two types of these, those that were changed regularly and applied to matters of permanent interest, and those that were limited to a particular operation.  The latter were used to order or report specific actions, to name places or features, groups of target, etc.

In the early years of the war theatres and formations often produced their own low level ciphers.  There was a need for three types of low level cipher:  

• Something for locations (ie map references), which could be used in the course of conversations with a little preparation.
• Something to authenticate another station to ensure it wasn't an enemy imposter.
• Something to encipher complete or partial message text.  

With any cipher the design and use problem is to balance simplicity with risk of compromise.  Any cipher used in the forward areas is particularly susceptible to compromise through capture.  This suggests that the domain of its keys should be limited, but maximum benefit is from having as many stations as possible using the same keys.  Also part of this equation is the frequency of key changing and their origin/distribution arrangements including how soon they are distributed before a change.

Authentication was achieved by use of challenges and response 'passwords'.  Typically a control station would challenge a new station joining a net and require it to respond with the 'pair' of the challenge.

In late 1943 Slidex was introduced as a general purpose code.  It provided a set of subject specific cards printed in a grid layout with words and short phrases appropriate to the subject, together with letters and numbers.  Each cell of the table was identified by a two-letter bigram from 'slides' along the top and down one side.  These slides were aligned in different positions for different messages.  It was used for messages classified up to Confidential.  

For messages above Confidential manual ciphering used 'one time pads'.  For example Meteor Telegrams were classified Secret and if sent by R/T or W/T had to be enciphered with OTPs.  These telegrams also had their own priority 'Meteor Immediate'.

A standard army wide low level cipher for map references was introduced with effect from the beginning of December 1943.  This was the Middle East map reference point code system.

Standard code names for roles were also introduced in 1942.  For example at any level and in any type of HQ or unit:

• a commander was always referred to as 'Sunray',
• an intelligence staff/officer was 'Acorn',
• a G staff/operations officer was 'Seagull',
• an A/Q staff/officer was 'Molar', and
• an artillery branch/representative of whatever rank was 'Sheldrake'.  

There were several others, this was all part of an effort to try and prevent R/T conversationalists, particularly officers, from using 'veiled' speech in an attempt to conceal what they were talking about and the level of the units involved.

Procedure Changes

A new phonetic alphabet was introduced in 1942.  Ack, Beer, Charlie, Don, · · · · was replaced by Able, Baker, Charlie, Dog, · · · · ·.  It was standardised with the US and lasted until 1955 when the ubiquitous Alfa, Bravo, Charlie, Delta replaced it.

A formal army wide and comprehensive Voice Procedure was introduced in 1942, it continued to evolve in some details and was aligned with W/T procedures.  For the first time the various standard phrases were established for use in all R/T traffic.  All R/T dialogues were opened with 'Hullo' and each individual transmission closed with 'Over' or 'Out'.  Other phases coped with poor signaling conditions, relay procedures, etc.  

Procedures to make enemy intercept more difficult were also introduced.  These included measures to defeat traffic analysis, mostly applicable to formation wireless nets, but including the use of wireless silence.  For example it became usual for formations in reserve to be on wireless silence.

Another measure to ensure wireless discipline were monitoring detachments using R107 receivers in signal regiment security sections at division and army level.  These had a programme of listening to all radio nets in their formation, recording breaches of procedure (particularly security) and bringing them to the attention of the offenders.  

AFTER WORLD WAR 2

From an artillery perspective changes were incremental.  Organisationally, the R Signals element in artillery regiments reduced to a rear-link detachment and all communications forward of RHQ became artillery operated.  Standard fixed call-signs were adopted within units throughout the army, instead of daily changing call-signs, with 'arm indicators' when elements of different arms were together on one radio net.  Voice procedure also continued to evolve. As previously mentioned the phonetic alphabet changed to the NATO one.

In the decade after the war a few new radios were introduced, particularly for use in the Far East and to make more use of VHF.  A new system of designating radios was also introduced, 'A' sets were manpack, 'B' were man-portable and vehicle mounted and 'C' were vehicle mounted.  Other letters were assigned to long range R Signals sets.  Vehicle mounted sets used 24 volt power supplies, and this meant that soft-skinned vehicles were either 'GS' (12 volt electrical systems) or 'FFW' (Fitted for Wireless - subsequently FFR) with 24 volt systems. 

The big change came in the late 1950's when the Larkspur range of VHF radios was introduced, although these radios still required the operator to manually tune them by listening to a signal tone.  UK adopted the practice of giving artillery its own VHF frequency band, which had minimal frequency overlap with the radios used in the rest of the army.  The Larkspur sets used by artillery were A42, B48 and C45, but to provide communications with their supported arm observers were equipped with A41 and C42 as well.   A41 and 42 were copies  of the US AN/PRC 9 and 10.  The B48 was primarily used for automatic re-broadcast by FOOs.  HF was little used except in the Far East and morse gradually lapsed apart from some specialist uses.  However, new HF sets were finally introduced in the mid 1960's, the A13 and A14.  Larkspur and the manpack HF sets were all replaced by the Clansman range starting in 1979.

Motor-cycle orderlies disappeared in the 1950's and line capabilities steadily reduced as VHF was introduced.  Line remained in use between CPs and guns.   Apparatus Loud Speaking (ALS) 21 was introduced to replace the wartime tannoys, it too had lights in the CP for each gun and enabled the gun to acknowledge orders by clicking the handset pressel switch.   B48 also became the standard set in SP guns (Abbot, M109, M107) and a new ALS23 could be used with both radio and line.  Abbot broke new ground by being fitted with induction loop communications to detachment members inside and outside the gun, although it wasn't an outstanding success.  Data communications between CP and guns arrived in the early 1970's with AWDATS (artillery weapon data automatic transmission system).  It could be attached to either line or radio, and displayed firing data at the gun, receiving it from the FACE (field artillery computing equipment) in the battery CP vehicle. However, it required good tuning of the B48 or line in good condition. FACE included a radio teleprinter that could produce punched tape, which could be input to FACE.  The radio teleprinter was used to receive meteorological data.

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