Royal Corps of Signals

Visual Signalling

Visual Signalling during the First World War Some of you may have noticed at our recent outing in Duncannon, the two tripods next to the command tent; one with a heliograph and the other with a signalling lamp mounted on them. You may have also noticed “Doc” and myself waving our arms about like a pair of eejits – no we weren’t trying to scare off the birds, we were in fact attempting to practice semaphore! The heliograph, a series of mirrors used for signalling Morse Code using sunlight (not for adjusting make up) and the signalling lamp (in this case, a Lucas lamp dating from the Second World War) were, together with semaphore flags, the principle means of communicating between formations of troops on or around the battlefield pre 1914. In fact, before the war, signallers were only trained in visual signalling and how to use effective cover and location to achieve the best means of communication.

When the BEF arrived in France in August 1914, these three methods of signalling were used, initially, to great effect, even though telephones and fixed line communication were in existence. Both systems were very effective where there was a static front line, but during moving warfare, they were found to be wanting. The telephone exchanges and lines in both France and Belgium were considered unsecure and ineffective by the British High Command, due to the inherent distrust of their allies and the lack of any coordinated framework for communication between the Armies. Additionally, there was a belief that the enemy could and would listen in to the network. Running lines to and from Regimental posts was not an option as these were moving too quickly to provide an effective network of fixed centres of communication. Furthermore, due to the speed of the retreat, many of the equipment, cabling and supplies required by the Signal Sections were lost to the Germans as they advanced. This was to prove costly during the first months of the war.

“The chief objection to visual signalling had always been the necessity for at least partial exposure on the part of the signaller in an advanced position, but men had been trained to make the most of the natural shelter available in the country. The Le Cateau district, consisting as it does of fine rolling downs, was ideal for visual purposes and extremely good work was done by the signaller's during the critical and closing stages of the battle. By the use of a blue flag, with the signaller in a ditch against a dark background, a station in a very exposed position in one bastion was kept in action throughout the fighting without being discovered by the enemy, although the latter came within 1,200 yards of the position. Signals were easily read by the aid of a telescope at the Brigade Headquarters 800 yards off. This case was typical of the initiative shown and by the use of such precautions visual proved adequate in many cases to deal with all messages of tactical importance.”

At the end of the retreat from Mons, the BEF stood to at the River Marne and the front line steadied:

“During the battle of the Marne which was fought in wooded country, forward intercommunication between division and brigade was by dispatch rider by day with, whenever possible, telegraph circuits during the night. For the latter, divisions made use sometimes of permanent line and at other times of cable from their replenished stocks. Brigades, however, having expended the greater portion of their cable, were practically restricted to the use of despatch riders and orderlies, reinforced, when the situation permitted, by visual. The country was heavily wooded and somewhat broken up by steepish ridges and valleys and was not normally suited for visual work, but prominent buildings were sometimes used with good effect. In one division, on the first day of the fight, heliograph was worked continuously for four hours from a brigade signal station in St. Cyr to Divisional Headquarters, and it was largely owing to the prompt seizure of all such opportunities by signal officers that an efficient system of intercommunication was kept up.”

The ensuing trench warfare meant that the communication system could now rely on the fixed line method. Unfortunately visual methods of communication were sidelined to such an extent that some of battalions sent their visual signalling equipment back to England!

There has been some confusion as to whether Morse or semaphore was used to send the signals. It appears that the trained Signal officers preferred Morse, however other arms of service, most notably the artillery used semaphore, as it was perceived to be faster. Morse can be sent by any visual signalling tool, whereas semaphore is only applicable to flags. Additionally, due to the very nature of “waving flags” the operator would be considerably more exposed for longer periods of time. Sense prevailed and the Morse method was adopted by all arms of service fairly quickly during the earlier stages of the war. It should be noted that communication between infantry and supporting artillery when fixed lines had failed was still carried out visually. Smaller signalling discs and shutter systems for daylight and trench lamps for night time signalling were extensively employed.

“By means of carefully worked-out schemes, artillery support was arranged for with the minimum of signalling and undesirable enemy attention was thus avoided. In one Infantry Brigade, communication from the front line to the artillery was carried out by flag by day and by lamp by night, two letters only being used, " O " meaning " Open fire " and " p " " Cease fire," each being repeated until the signal had produced the desired effect. The system worked with such smoothness that artillery support in the form of rapid fire on certain pre-arranged areas, could be relied upon by day or by night within a period of 20 seconds of the time when the call was first made.”

On the 21^st March 1918, the German Army launched Operation Michael, the final German offensive of the war. The German stormtroopers were able to push through the thinly defended British front line with devastating effect, aided throughout the morning by thick mist mixed with gas, leaving the main German force to mop up any pockets of resistance. Regular fixed line and visual communication posts were targeted early on and as a result the communication system broke down that morning. As the mist cleared towards the afternoon of the 21^st, visual signalling was used to a great extent. Between Brigade and Division in the second and third line the surviving visual posts comprising heliograph stations were able to maintain communication.

“It was the first time that visual had been given a great opportunity on the Divisional-Brigade line of communication and in this and the succeeding days long distance work was somewhat hampered by the reduction that had taken place in the number of heliographs issued to forward troops. Their place was, however, fairly successfully filled by the Lucas lamp which proved an efficient substitute over most of the distances involved.”

Formations retreating at random could only obtain touch through their wireless sets, or by the establishment of visual stations. For lateral communication, especially, visual was invaluable. In the rear areas the Lucas lamp was the main means used, with the heliograph as substitute on isolated occasions. Forward, flags were used a great deal, but the folding shutter attached to a bayonet fixed on the end of the signaller's rifle was the favourite method. Pocket electric torches were again used with success over short distances. In one Division, visual signalling was the sole means available between Division and Brigade for three days and 50 messages a day were processed by the visual stations.

Extracts from “THE SIGNAL SERVICE IN THE EUROPEAN WAR OF 1914 to 1918.(FRANCE)” - R. E. PRIESTLEY, MC, BA. (Late Major, R.E.).