The adoption of indirect fire as the main methodology necessitated the need for accurate mapping and survey in order to establish the exact location of our own guns, and to provide a mechanism to know the enemy target. At the battle of Mons, british artillery was ofter located near the infantry positions, shrapnel direct fire augmenting their rifle and machine gun fire. By November 1917, Cambrai became the first bnattle which relied on wholly predicted fire.
In addition to the survey role, the location of enemy artillery for counter bombardment became another essential role of the surveyors.
As ever the Long Long Trail provides essential information: http://www.1914-1918.net/re_survey.htm
I have Peter Chasseaud's Artillery's Astrologers - A History of British Survey and Mapping on the Western Front 1914-1918 on my reading list;
I came accross a paper to presented at the RA Historical Society which provides an good overview
Source: ROYAL ARTILLERY HISTORICAL SOCIETY A Presentation by Brigadier Fraser Scott MA
A Royal Engineer Ranging Section was sent to France in November 1914. It fixed enemy batteries using air or ground observers. Aeroplanes had no wireless so enemy batteries were fixed by the pilot dropping a smoke bomb over one. This was intersected by ground observers which meant that the observers had to be surveyed in. So too had the guns which were to engage them. This was the nucleus for surveying in the artillery. The aircraft were soon issued with wireless so that they could report enemy battery positions on the map. And, as artillery ammunition was in short supply, they needed to reduce the amount used in adjusting fire onto targets and in registering them. This meant surveying in our own battery positions. At the start of 1915 the Ranging Section had a strength of only 19, then in April 1915 it became the 1st Ranging and Survey Section RE under GHQ and a circular went out to Army and artillery commanders:
“The primary objects of this Section were:
In addition to the above, the Section has, on several occasions, done useful work in determining the coordinate positions of heavy guns or batteries and supplying bearings and ranges to various conspicuous objects round them” (this was the original of the “bearing picket” ).
The Ranging Section started flash spotting in the winter of 1914-15 using a bearing and range from the angle of depression (the observer was in a commanding position higher than the enemy battery). The results were poor due to the state of the maps (for range accuracy you had to know the difference in height between the observer and the gun). They also used the time from flash to bang to determine range but this wasn’t accurate. Allenby, who was commanding the Third Army, authorised a flash spotting course to be held for 12 officers to select five to be in charge of OPs which were being constructed. Men were provided by artillery units, and flash spotting started. On the Somme front in October 1915 (the front line ran east of Albert) flash spotting, posts named after London music halls were chosen to give as good a coverage as possible..
At this time enemy gun location was mostly done by air reconnaissance which did not satisfy the commander of Second Army who ordered, in October 1915, that
This was the start of a proper counter-bombardment system.
Sound ranging began, for the British, when Lawrence Bragg, a Territorial RHA officer and Nobel Prizewinner, was sent to France in October 1915. The French and Germans had already started. Lucien Bull in Paris had developed a recorder based on his work on recording heartbeats. He proposed using an Einthoven string galvanometer with the movement of the strings, and that of a timing device, recorded photographically. Bragg got a Bull recorder and started to sound range just south of Ypres in the Second Army area. He had a mathematician, and electrician, an instrument maker and five others. He got going and persuaded the authorities to add more recorders. He had worked at Manchester under Rutherford and got eight other scientists from there. But the real problem was the microphone type – carbon granule – this was excellent for high frequencies but useless for the low frequency of guns firing (40 hertz or 40 cycles per second).
In 1916 things started to get more settled. In February the surveyors were organised into Field Survey Companies RE, one per Army. Each Army had an Observation Section (for flash spotting) and a Sound Ranging Section. So the field survey companies were responsible for:
Fixing British batteries - topographic section
Map drawing, printing and distribution - map section
Flash spotting - observation section
Sound ranging - sound ranging section
all under a Company HQ which also had a compilation section responsible for artillery intelligence.
1916 saw the system develop - more men were made available so that flash spotting could operate with their posts manned effectively all the time. There was also a Group HQ connected to the posts by telephone exchange so that the posts could communicate to each other too. But it was still difficult to know which flashes were which. The bearings had been measured using theodolites but these presented an upside-down image. They were replaced with Apparatus, Observation of Fire, Instrument used by Coast Artillery; it had a spider’s web graticule, black by day and lit, at night, by a bulb controlled by a resistance. If the flash was dim you decreased the brightness: if it was bright, or you were only seeking a sky reflection, you made the graticule brighter so you only saw the core of the flash and could take the bearing to it.
The telephone lines were provided by the Royal Engineers Signal Service: they could be on the ground, on ‘cosmic’ poles or buried (above ground ones were more vulnerable but easier to repair, buried ones lasted longer but harder to mend). In May 1916 Hemming had a bright idea on how to ensure that the posts were observing the same flash – it was to have a telegraphic key in each post so that when an observer saw a flash he pressed his key and lit a lamp in the HQ – but there wasn’t enough current to light the lamp. He wrote to Bragg who suggested a sensitive relay so when Hemming went on leave he went to Lisle Street in London and bought six relays, keys and buzzers. Coming back after only four days of a fortnights leave (his fellow officers thought he was mad), he mocked up a system that worked. The GPO built Flash & Buzzer Boards for all the flash spotting bases and flash spotting became effective. And in 1916 a School for Observers was inaugurated.
Sound ranging too improved. Bragg had noticed how, when sitting on the privy of his billet, he was lifted when the noise of a gun firing arrived. This indicated that the gun sound moved the air. Corporal Tucker had arrived in this section: he had experimented at Imperial College on the cooling of hot platinum wires by air currents and they thought that such wires would respond to the gun sound but not to higher frequencies. They got some thin wire, put it across a hole in an ammunition box, connected it to their recorder and, when a German gun fired, there was a large ‘break’ in the film record as shown in this diagram of a film showing the breaks and the timing marks:
As Bragg had written “ it converted sound ranging from a very doubtful proposition to a powerful practical method. They also realised that, if the microphones were set out regularly, it was much easier to pick out the signal from one gun, or from a battery. A map of the bases in 1916 shows the section bases are lettered ound rangers are physicists and serious) and the flash spotting posts named after the villages they are near – Lavender for Lavendie – Bullrush for Bully etc.
As the battle fromt moved, the locators had to move forward which the flash spotters did post by post. The sound rangers now had the Tucker microphone, which meant that out own shell bursts could be located so far out that CB fire could be adjusted accurately onto an enemy battery thus avoiding any errors due to wind etc. Tucker himself was commissioned and sent to the Artillery School on Salisbury Plain to form an Experimental Section to work on sound ranging. And early in 1917 they had a series of sound ranging conferences to disseminate new ideas. Ludendorff, directly under Hindenberg, issued an order summarised:
He also wanted to have a British sound ranging apparatus captured.
For the Battle of the Somme each Corps had a Counter Battery Staff Officer to make sense of the gun location now being obtained. He reported up the Gunner chain of command. Besides the CBSOs there were also Royal Artillery Reconnaissance Officers (RAROs), which caused some confusion. Hemming became the RARO for VI Corps: he couldn’t order any counter battery fire but had to deal through the CBSO, Colonel Fawcett the explorer, who would consult his ouija board to see if Hemming’s location should be “confirmed”. However, British CB had an effect on the German artillery tactics. For them protection gave way to concealment and positions changed with a rapidity that made our hostile battery lists out of date. The CBSO dealt with immediate problems and the RARO with longer-term assessments. Proper CB plans were now being made. For this First Army’s attack CB destroyed or neutralised 90% of the German batteries.
The Germans withdrew to the Hindenberg Line in March 1917. R Sound Ranging Section noted that the Germans were shelling inside their old front line but didn’t report it until the Corps Commander rang up to enquire. T Section made no locations west of the Hindenberg Line but didn’t report this for 24 hours. So they all had to move eastwards. Studies were made of locating accuracy: 4th Field Survey Company found that of 230 German battery positions 86.5% had been correctly located. More sound ranging sections were authorised.
It took about two weeks to install sound ranging sections due to the time taken to lay the lines (the ground was in a bad state). Studies were made to improve mobility which were to be useful later.
In June 1917 First and Second Armies instituted report centres to warn all locating units of activity. These centres were connected to the Flying Corps, balloons, flash spotters, sound rangers, anti-aircraft and wireless stations as well as to corps report centres, corps heavy artillery and divisional HQs.
Before the Messines battle in June 1917 the British put in a false attack to draw German fire so as to get locations. After the battle it was found that the sound rangers had accurately located over 93% of the German battery positions so the Germans had to adopt various ruses - alternative positions, dummy flashes, wandering guns etc. As a result the British CB wasn’t as effective as it had been especially in the flat country around Ypres.
After the Passchendaele battle, the Canadians criticised the locators for being too far back, the reason being the Signal difficulties. They recommended transferring them from intelligence to artillery command. GHQ immediately put them under the Royal Artillery for tactical purposes and this must have influenced the post-war decisions. The Corps HQRAs now directed them.
Schools of instruction were established: each Army had an artillery school and there were also an Observation School for flash spotting and a Sound Ranging School.
In November 1917 the battle of Cambrai became the first battle when all the artillery fire was to be predicted, with no preliminary registration,in order to achieve maximum surprise. All the heavy and siege batteries were surveyed in and provided with bearing pickets as well as some of the field ones. 90% of the hostile batteries had been correctly located, mostly by the locators. Besides this, specially trained mobile flash spotting and sound ranging detachments followed up the advancing troops: one base was in action 56 hours after zero. however, the Germans counterattacked and some apparatus had to be thrown into a pond to avoid capture.
When the Russians collapsed, Germany could now reinforce their Western Front. The focus on the western front was to prepare for defence and reserve bases were prepared. An an experiment was done which showed that a long base further from the enemy was better than a short one near him.
Hemming had a great moment as RARO when, in March 1918, Field Marshal Haig visited VI Corps HQ and came to the artillery office.
He asked Hemming “Could the Germans attack tomorrow?”
Hemming said “I don’t think they could”.
“Because we had one gun per three yards of front at Ypres and he will want more. I’ve only found one third so far though more have just moved in”
“All right, as soon as you have found half of the missing batteries send me a telegram”. Hemming sent the telegram on 18th March and the offensive started on 21st March. He used air photographs for this as the Germans had copied us by using predicted fire.
When the Germans attacked the locating lines were cut and no locating could be done. As it was essential to avoid the sound ranging apparatus and the flash and buzzer boards being captured, the locators moved out and through the new British front. As each post only had a two-wheeled cart much had to be left behind or destroyed. Some were taken prisoner: others found themselves formed into ad hoc defence forces digging trenches as infantry. The situation stabilised, gun survey done and locating bases established: In May Bragg and Hemming were brought back to actual locating to work on the GHQ Defence Line, our most rearward position.
In July 1918 the Field Survey Companies became Field Survey Battalions, commanded by Lt Cols, representing the increased strengths. And in July the Allies (the Americans had now joined in) started their offensive using the now established predicted fire. For the battle of Amiens in August the locators were ready to move with the attack and the flash spotters had wireless (attempts to do a radiolink for sound ranging had not been successful).
During the Hundred Days leading up to the Armistice the locators followed up the Allied advance as best they could. Among their problems were deaths from Spanish flu. It is worth noting the batteries located by 4th Field Survey Company/Battalion:
By the end of the war there were field survey battalions in France, Salonika, Egypt and Italy. What sort of people had been involved? All sorts: they volunteered from the rest of the Army and were recruited from universities. They welded themselves into small groups with a remarkable esprit de corps (even though there was no formal corps). The posts operated on their own with little supervision by officers (the officers were too few and too busy). The nature of the war was such that many groups integrated themselves into the local populace aided, for the flash spotters, by the fact that the positions of their observation posts were dictated by the command they had to have over the countryside so a post was used for months, if not for years. For example Lavender, in Laventie Church, was first used in 1915; 2 Field Survey Company took it over in March 1916 handing it over to 1 Field Survey Company in July and stayed until the German attack in April 1918 (which destroyed the church). But by August 1918, the flash spotters were back in Laventie. Chasseaud wrote in his book Artillery Alchemists: “The men of the group … were practically villagers in their own right”. Here is a drawing of one of them in his billet:
Their self-reliance was well demonstrated in the German 1918 attack: many posts were cut off from their HQ so they had to make their own decisions as to when and where to go.