Military Mapping in the Revolution


We do not have an actual statement of the use to which Hugh, earl Percy put his copy of the Jefferys-Green Map of the most Inhabited Part of New England. It is not mentioned in the small amount of Percy’s correspondence, whether military or civil, that has been published; it is possible that background information exists in the Percy family archives at Alnwick, Northumberland. In order to understand how Lord Percy might have used the map, it is first necessary to understand the nature of military map making and map use in the late eighteenth century. In this respect, we have necessarily relied on Harley’s (1978) ground breaking analysis of military mapping during the Revolutionary War.

Military Mapping in the Revolution

In summarizing the various mapping activities by the American, British, French, and German combatants during the Revolutionary War, we must reconcile two seemingly opposing factors.

On the one hand, military mapping did not comprise a mass of unrelated, isolated cartographic episodes: “The study of maps and plans of the military engineers of the eighteenth century . . . reveals a cartographic genre which is truly international: in France or in Britain, in India or in North America, the plans exhibit sufficient common traits of technique and design to be logically intelligible in the light of diffusion of a basic style by a highly mobile and professional group of map makers” (Harley 1978, 65-66). Most mapping was undertaken by the military engineers, who were in general the most educated of eighteenth-century soldiers and who specialized in large-scale surveys for fortification. Regardless of their nationality, military engineers were trained from the same, or at least similar, textbooks. The shift of European warfare, increasingly evident after 1700, from the old strategic emphasis on static fortresses to a new strategic emphasis on mobile armies, steadily increased the need for regional geographical information and led to the training of non-engineer officers in the techniques of map making. As with the education of military engineers, the new military academies pursued remarkably similar curricula. It is important to stress that only a portion of officers were trained in the new academies. Most junior infantry and cavalry officers were concerned primarily with drilling their troops in order to be able to carry out the tactical requirements of the battlefield. Throughout the eighteenth century, strategy remained the preserve of senior regimental and staff officers. A few of the more able junior officers did however take an interest in larger strategic issues and had sufficient education (often self-taught) to make maps and surveys. By and large, we should not exaggerate the spread of cartographic literacy among the army at large (Edney 1994c).

On the other hand, there was no single phenomenon of “military mapping” in the eighteenth century. The engineers made, and general officers used, a wide array of maps. The variety of mapping is clear from the collections by Nebenzahl (1974) and Marshall & Peckham (1976), and from the explorations by Harley (1978). The following categorization is based on the divisions of warfare that were widely acknowledged during the eighteenth century.* However, those divisions were not themselves distinct, and so overlapping map categories are inevitable:

a) Fortifications

Fortification plans cover a wide range of items ~ plans in text books, usually of idealized fortifications; construction plans for new fortifications; and, plans of existing fortifications ~ but all possess the same characteristics. They are large-scale and highly detailed, reminiscent of architectural drawings. Text book plans were printed, of course; the rest were uniformly left in manuscript. Production of such plans had, since the fifteenth century, been an integral part of the duties of military engineers.


This overlapping category encompasses tactical plans of fortifications under siege, either contemporary to the siege (manuscript) or distributed afterwards (often printed). These have the same characteristics as group ‘a’.

b) Tactics

Tactics is the organization of military activity at the level of actual combat. Tactical maps thus comprised large-scale, detailed maps of forts (group ‘a/b’) or of battle fields. While some maps were made of potential battlefields, most of these maps were either sketches to show the order of battle (how the various units were to be arrayed) or, most often, they were record and ‘memorial’ maps made after the battle. While most such maps were in manuscript, the last sub-category also included numerous printed battle maps, often published in newspapers and military texts (Nebenzahl 1975).

c) Strategy

Strategy is the organization of military activity across a wide region; it is especially concerned with the coordination of the movement of troops in an intricate dance. Generals had, since the fifteenth century, used small-scale, and not particularly detailed, chorographic maps to envision a wide extent of territory. Such general maps effectively formed real-life chess boards across which the generals could imagine competing armies marching back and forth.

In the case of Percy’s map, the regional map was in fact a commercially printed general reference map. When such maps were not readily available, generals had them compiled by engineers (or, on occasion, a cartographically trained infantry officer); these maps were sometimes given at a later date to commercial cartographers to be printed, but many remained in their original manuscript form.

A further category of strategic, movement maps were the maps made of particular roads or routes. The story of Arnold’s failed expedition to Canada indicates the need for generals to know more about the details of the route to be marched by troops: is the road itself suitable; are there places for encampments; can artillery be hauled or do the pieces have to be man-handled; can the rivers be crossed; are there potential ambush sites? In the eighteenth century, troops were always moved against a background of variable information. Army columns often “blazed trails” and recorded their routes for later use (see the several route maps made by Rochambeau’s Fayette’s soldiers, in Rice & Brown 1972). Alternatively, generals sent out reconnaissance parties to map out the roads through a territory (see below). Route maps were thus detailed, large-scale, and usually long and thin (see Edney 1997, 91-96). Such road maps were, in the 1700s, the primary source material for the more general regional maps which generals had constructed.

A final type of strategic map was relevant to the combatants in the American Revolutionary War, specifically the regional topographic maps. Such maps are similar in content to the large-scale plans of fortifications and battle fields, in that they show hills and valleys (i.e., the topography). The principal difference is that topographic maps are non-specific in their spatial framing; rather than focusing on just the one fortress or battle field, regional topographic maps encompass large swathes of territory. They are necessarily large and unwieldy, but they give a comprehensive and highly detailed image of landscapes to generals and lieutenants alike. When sufficiently detailed, they can even be used for tactical purposes. Needless to say, the construction of such maps is a laborious and expensive process. Between 1765 and 1775, the British embarked on a program by which coastal areas were surveyed in great detail, by Samuel Holland and William Gerard De Brahm. (It is no coincidence that both men were Dutch/German engineers trained in the continental schools of “topographical engineering”; the British had no native pool of such skills.) Many of the resultant maps circulated in manuscript and printed form during the Revolution and provided essential strategic information. Overall, however, regional topographic surveys were not common during the Revolutionary period.

d) Logistics

Logistics is the organization of the distribution of military supplies, everything from foodstuffs to heavy artillery. Most mapping associated with logistical activities was related to the organization of actual movement (diagrams of the order of march) or of storage. The “quarter master general” of each army not only kept record of route maps so as to be able to direct the movement of troops and supplies, he also kept plans of most encampments and forts for the purpose of organizing and structuring their spaces. In this respect, logistical maps again tended to be large-scale and detailed in character.

* Rather idiosyncratic classifications were made by Guthorn (1972, 6) and Cumming (1974, 57). The classification presented here is an extension of Harley’s (1978, 1-44) more rigorous, three-part categorization of fortification cartography, battle maps, and the “cartography of military movement.”

Summary of the Range of Military Mapping

Overall, the kinds of military maps that dominant both the careers of the military surveyors and the present-day archives were the fortification plans and tactical maps. From studies of the cartographic work by Bernard Romans (Diamant 1985), Claude Joseph Sauthier (Babinski 1997), it is apparent that the smaller-scale regional mapping usually formed only a small part of the duties of military cartographers. Similarly, catalogs of the map collections of Sir Henry Clinton (Adams 1928) and of William Faden (Catalogue 1862) are heavily weighted towards highly specific, detailed maps. The records of Rochambeau’s army seem to reveal the production of no general, regional maps at all by French military cartographers (Rice & Brown 1972). The overt specificity of military mapping had significant implications for the character of that mapping. Highly specific maps will, by definition, have little utility beyond their original purpose. Only a few copies of any particular map were usually needed. In such circumstances, it was not cost effective to print the maps. They generally remained in manuscript; new copies were made by draftsmen when needed. This equation was broken only when the military map served some broader, public purpose. Sauthier’s general maps of New York had a certain popular appeal to members of the public who wanted to know about that province, and they were ultimately published in London (Babinski 1997). But here again, the published general maps were far outweighed by the publication of battle maps to inform the public on both sides of the Atlantic of recent developments in the war (Nebenzahl 1975).

Percy’s Use of his Map

All told, the military purposes to which Percy would have applied his copy of the Map of the Most Inhabited Part of New England were obviously limited. One point is clear: the map was simply too small-scale and undetailed to be used in the tactical planning for April 19th, 1775. This is not to say that either Colonel Smith in the main column, or Percy in the relief column, did not have any idea of where they were going.

It was common (even after the first powder alarms of September 1774) for British officers to exercise their horses by riding away from Boston; they were under standing orders when they did so of not wearing any arms. (Accordingly, when officers were sent out ahead of Smith’s force to intercept provincial messengers, notably Paul Revere, their wearing of arms served only to signal that the British were about to launch a raid.) To some degree, then, the officers could be expected to know the country for themselves, certainly south of the Charles River and in proximity to Boston Neck. Furthermore, General Gage had taken the precaution of sending out two officers from the 10th Foot ~ Captain John Brown and Lieutenant Henry de Berniere ~ to reconnoiter the roads first to Worcester (deemed too far) and then, in March 1775, to Concord. Brown’s and Berniere’s report to Gage made it clear that the shorter, southerly road to Concord went through close country with many woods and ridges to hide the provincials; the northerly road via Menotomy and Lexington, however, was longer but was more open and so safer to cross (Fischer 1994, 80-85). When he eventually sent out the raid on Concord, Gage accordingly ordered it to follow the northern route.

The local knowledge derived from these reconnaissance surveys was further augmented by information gleaned from loyalists and spies. Thus, Gage was able to give Smith a map of the town of Concord, showing the buildings and identifying the food stores and arms caches in each (see Gage’s orders to Smith, reproduced by Tourtellot 1963, 103-4). This information came from several sources, most notably Dr. Benjamin Church, a member of the Provincial Congress and the Committee of Safety, who apparently needed money to keep a mistress in Boston.

Yet even such detailed information was insufficient for moving the troops through the country. For example, Percy’s own knowledge took the relief column from Boston Neck to the bridge across the Charles River at Cambridge. But at that point, Percy found himself at a loss and had to ask directions to Lexington (apparently from the only person on the street, an absent-minded tutor at Harvard College who would probably not have answered had he been paying attention and heard the call to arms: Fischer 1994, 240-41). The issue here is that the movement of troops in eighteenth-century warfare relied heavily upon local informants and guides. Local informants were already being supplanted in Europe by regional topographical surveys, when available. But without such surveys to provide a useful middle-level knowledge of the landscape, Percy and his fellows had to resort to the more flexible and capricious knowledge sources available.

We come back, at last, to Percy’s use of his map of New England. Given the nature of geographical information available to him at the time, and given the military functions of contemporary maps, we can only conclude that Percy used the Map of the Most Inhabited Part of New England as a way to conceptualize the strategic theater of war in New England. Looking at this map spread out on a table-top, Percy had the best possible cartographic image of the whole region. The map lacked many roads, however, and so Percy had to add on the basic lines of several routes. The routes themselves bear a close similarity to several of the specific maps of the region, such as John DeCosta’s July 1775 plan of the battles of Concord and Lexington. But the presence of the routes on the map serve as guides not to action, but to conception. This is a map that tells you not how to do something, but rather what can be done. The Jefferys-Green map, strengthened by Percy’s annotations, might be construed to have been a test of the generals’ skills and daring. It held out numerous potential courses of action, none of which the British commanders took. Instead, they sat behind their fortifications, protected by their ships’ guns, for nine months after Bunker Hill before finally evacuating the city. That is, the British failed their cartographic, conceptual test.