Battlefield Geometry: Guns, Grids and a ‘Revolution in Military Affairs’

A graphic depiction of battlefield geometry for the artillery; a French canevas d’ensemble, showing trigonometrical points and directions repères (bearings marked on terrain features and used by the artillery for picking up an accurate line-of-fire).

Battlefield geometry in numerical form. List of coordinates of trigonometrical points issued for the use of the artillery. This list was produced by the Groupe de canevas de tir of the French Sixth Army, in the Chemin-des-Dames sector, 1917.

German aerial photograph of Fort Moulainville taken on 13 March 1916, during the early stages of the Verdun battle, showing the quality and clarity of photographs used for tactical mapping and intelligence.

Aerial photograph of Bois-en-Hache sector, Vimy Ridge, taken while snow was lying on the ground in early 1917, showing how clearly trenches and other detail show up. Snow also made it easy to identify barbed wire entanglements, distinguish used from unused trenches, and showed blast-marks from active batteries.

In dry and technical terms, a topographical map may be described as a two-dimensional representation of a three-dimensional part of the Earth’s surface, which implies a projection of some sort. However, it is perhaps better considered as a picture or model of the landscape or terrain which enables the user to grasp its features and land-forms, and their relationship to the user and to each other. The spatial relationships between points are formalized through their underlying relative coordinate positions in a three-dimensional matrix, comprising, for example, latitude, longitude and height above datum, or, to put it another way, x, y and z coordinates. For surveying and military purposes before and during the First World War, Descartes’ x and y coordinates, with a specified origin and orientation, together with height data (z), based on a chosen datum, were generally used by all participants.

Geographical coordinates are a way of defining positions on the Earth’s surface. Claudius Ptolemy (AD 90–168), the Graeco-Roman mathematician, philosopher, geographer, astronomer (he used Babylonian astronomical data) and astrologer of Alexandria in Egypt, was the first person known to have used the concepts of latitude and longitude to do this. Map projections are systems of converting the spheroidal surface of the Earth to a flat plan, and projections vary according to the intended use. For example, Mercator’s projection, being orthomorphic, does not distort angles, so is adopted for sea and air navigation. Courses can be ruled as straight lines on the chart and then set on the compass for the helmsman or pilot to follow.

Topographical maps have proved vital in war, particularly, in the twentieth century, for artillery work. The First World War has often been described as an artillery war, and for scientific gunnery maps had to be as accurate as possible. Their underlying and invisible spherical trigonometry and triangulation were made visible in the form of a grid and a dense network of fixed points. For laying out lines of fire, grid north supplanted magnetic north, as the vagaries of compass bearing were replaced by the certainties of bearing pickets (or the French directions repères, lines of measured bearings actually marked on terrain features) and astronomical observations, and orthomorphic projections were introduced which maintained shape or bearing. All these techniques facilitated the widespread adoption of the gunnery technique of ‘predicted fire’, which enabled a barrage to be opened with a crash without previous registration of targets. This is why the surveyors were called by the gunners ‘the astrologers’. A new battlefield geometry was thus created, in which the trigonometrical framework was amplified by new control points, hachures were replaced by surveyed contours, all batteries and targets were fixed to the survey grid, and surprise restored as a principle of war. Maps and survey became part of an integrated modern weapons system, which in turn constituted a revolution in military affairs.

The First World War was, more than any previous conflict, a war of maps. Millions were printed during the war, as is shown at the end of this introduction. Every country was equipped with appropriate maps for a war of movement, but the rapid emergence of trench warfare changed the nature of the conflict and therefore of the nature of the required survey and mapping; position warfare implied precision shooting on pinpoint targets, and artillery survey became paramount, particularly for the predicted fire which reinstated surprise as a key factor in successful operations. Paradoxically, the shock effect of a ‘crash’ concentration required less accuracy. Most survey work was done, directly or indirectly, for the artillery, and as a leading British survey officer (M. N. McLeod) noted, ‘In the battles of 1918 the gun was king and the theodolite and plane-table its unadvertised but indispensable ministers.’

In August 1914 all participants entered the conflict with stocks of small- and medium-scale maps with small staffs for distribution but, as the nature of the impending war had only partially been divined, practically no survey support during operations. While France and Germany had envisaged the need for large-scale maps and survey operations for the capture of enemy frontier fortresses, they were not prepared for the semi-siege operations that became the norm. Britain had not prepared in any serious way for siege warfare, and had to adjust more to the new situation. The crucial need for such operational support – particularly artillery survey and air survey – immediately became apparent, and each country began to build up a field survey organization commensurate with the operational requirements.

A key aspect of the survey revolution was aerial photogrammetry – plotting detail from air photographs. This was realized by both sides as soon as the war changed from movement to static conditions in the late summer and autumn of 1914. From the moment the Germans dug their first trenches on the Aisne heights in mid-September, the Allies had to acquire photographic cover of the concealed zone behind the German front trench, where artillery batteries, trench mortars, rear defences and transport and reserves were located. As defence systems proliferated, this need became more intense, for intelligence, artillery survey and mapping purposes. Both sides rapidly developed aerial photography and struggled to devise or adapt methods and technologies for rapid and accurate plotting from air photographs.

The geographical products of the survey organizations included line maps, photo-maps, plans, sketch maps, trigonometrical lists, air photographs (vertical and oblique), horizontal (terrestrial) stereo photos, panorama photographs, drawn panoramas, hostile battery position and target lists, artillery (battery) boards, etc.

Taking British military maps as an example, the basic large-scale topographical map was used as a background for the overprinting of tactical and administrative information. The most obvious tactical overprint was that of the trenches themselves, both British and German. For the years 1915–17 most British maps, for security reasons, only showed German trenches. British trenches only appeared on ‘secret’ editions, of which tiny editions were printed, mostly for staff use; front line troops rarely saw them. Other significant overprints were ‘hostile battery positions’, ‘barrage’, ‘situation’, ‘target’ and ‘enemy organization’ maps. It was important to show all aspects of the enemy defensive and offensive preparations, so that operations schemes could be worked out, barrages and neutralizing fire planned, and tanks and infantry would know the exact position and nature of the enemy dispositions. On a scale as large as 1:10,000, which was the most common for infantry and field artillery, these tactical features, down to individual machine gun and trench mortar emplacements, could be indicated with precision.

Techniques were developed for plotting topographical and tactical detail onto the map, with great accuracy, from aerial photographs. The map was itself the result of the refinement of survey techniques over four years of war, the most important parts of the process being the harmonization (not seriously undertaken until 1918) of the pre-war trigonometrical systems of France and Belgium by the British survey staff, the compilation of cadastral and other large-scale plans onto this trigonometrical framework, the plotting of additional detail from aerial photographs, and the coordination of existing levelling systems and ways of depicting ground forms.

Many parts of Europe, however, and most of the rest of the world, were not covered by accurate, large-scale mapping. In these areas, including the Ottoman Empire and Africa, the enlargement of small-scale maps, or painstaking compilation of new maps from a multitude of sources, had to be undertaken. These sources included map archives, boundary commission reports, Admiralty charts, explorers’ and travellers’ route surveys and notes, and official but clandestine surveys such as those by the ‘pundits’ of the Survey of India across the frontiers into Afghanistan and other neighbouring territories. There were parts of Arabia (the ‘empty quarter’) and Africa which were barely mapped.

In this context, military surveys during the First World War made a useful contribution to the mapping of certain areas, and some of those maps, particularly those compiled from aerial photographs by the British 7th Field Survey Company in Egypt and Palestine, and by the Tigris Corps mapping organization in Mesopotamia (Iraq), represented a notable advance in the mapping of those territories. For example, Map TC4, issued to troops with Tigris Corps Operation Order No. 26 dated 6 March 1916, was compiled from old pre-war small-scale maps of the river, Royal Engineers reconnaissances, air reports and sketches of the ground inland.

Survey, map compilation and printing organizations were created and expanded on all fronts as the war continued. Again taking Mesopotamia as an example, as air cooperation improved, and in order to provide the army with maps of the completely unsurveyed enemy-occupied areas, a Map Compilation Section was provided by the Survey of India in June 1916 to support the attempt to relieve General Townshend’s force at Kut. As the work of the Section rapidly increased in its technical aspects and operational value, it was more closely linked with GHQ and the RFC, and a Survey Directorate was created in early 1917 to bring all aspects of mapping under one control. Between June 1916 and November 1918 the Map Compilation Section printed 931,441 maps, covering between 103,840 and 143,983 square miles (the sources disagree) at various scales. Of this area, 2,263 square miles, and 120 map sheets, were mapped from air photographs. At the larger artillery and tactical operations scales of three-, six- and twelve-inches to the mile, 180,211 copies were printed in up to three colours.

As with munitions and other forms of war work in a time of manpower shortage, women were brought in to assist with map production, particularly in the Ordnance Survey at Southampton and its out-station, the Overseas Branch (OBOS), in France. They were mainly employed in feeding paper from the high ‘feed-boards’ of the lithographic printing machines into the grippers which took the sheets around the cylinder and onto the inked stone or zinc plate carried on the reciprocating bed of the press.

 

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