map in detail, places it in the context of his other works and his times, and compares it with other maps that analyze Napoleon’s campaign. Edward Tufte, the noted statistician, regards Minard’s map as probably the best statistical graphic ever drawn. What makes this celebrated map so special? The answer requires a closer look. Figures 2-1 and 2-2 display two versions of the map, the original and an adaptation translated into English and redrawn to explain content.
Figure 2-1 The “Carte Figurative des pertes successives en hommes de l’Armée Française dans la campagne de Russie 1812–1813,” translated as: “The Figurative Map of the successive losses of men of the French army during the Russian Campaign 1812–1813.”
2.1 The map
Cartographers classify Minard’s work as a flow line map, or flow map for short. These maps overlay lines, typically punctuated by arrowheads, to indicate both the direction and route of movement across a given territory. Origin-destination maps vary slightly from this norm, because they emphasize the connection between locations, rather than the flow from one location to another.
In contrast to flow maps, origin-destination maps’ paths are highly structured, and do not use arrowheads to indicate direction. Both types of maps illustrate the volume of flow by varying the thickness of the path line’s shaft, some by gradually trimming the thickness of the shaft, others by splitting the shaft into sections and giving each section its own uniform thickness. Minard’s map, for example, splits his line into sections to indicate the ever-diminishing size of Napoleon’s army. With just a glance, flow line maps give readers an immediate impression of both the direction of something in motion and also the volume of its flow, as Minard did in his studies of transportation, commerce and, in this case, war. True to form, Minard split his line into sections to indicate volume. However, it appears that he did not use arrowheads. At first glance, someone who was not familiar with the topic might not be able to interpret the direction of the movement. However, the text below the map’s title explains that color indicates direction: “The red (which appears orange in figure 2-2) designates the men who enter into Russia, the black those who leave it.”
Ideally, good maps should immediately be clear to the reader. To understand their content, however, French cartographer Jacques Bertin argues that readers must adopt a traditional three-step map-reading approach (Bertin 1983 [1967]). First, readers should execute an external identification of the map, asking what the map is about. Reading the title of the map can often answer this question. Minard’s title is rather long: “Figurative Map of the successive losses of men of the French army during the Russian campaign 1812–1813.”
The second step calls for internal identification, how the topic is displayed. This requires reading the legend to find out how symbols represent the elements of the topic and what scale is used. It also calls for a study of the map’s bibliographic data, which provides information about the map’s author, its publisher, and its age. Minard inscribed this information immediately below the title: “Drawn by M. Minard, Inspector General of Bridges and Roads, in retirement. Paris November 20, 1869.” However, he relegated the information about the publisher and printer, in small print, to the lower left- and right-hand corners of the map: “Paris: Regnier et Douret.”
The map bears no legend that people would generally understand, however, the extensive text below the title takes its place. Explaining the width of the flow line, it states: “The number of men present are represented by the width of the colored zones at a rate of one millimeter for every ten thousand men; they (the numbers) are additionally written across the zones.” In the maps in figures 2-1 and 2-2, this scale is no longer correct, because both have been reduced from their original size (63 × 25 cm), however, the numbers written along the segments mitigate the problem this creates. Moreover, the line’s colors communicate information about direction: “red” (which appears orange in figure 2-2) indicates east into Russia, while black indicates west out of it. Minard also describes his data sources, in the same text block, something that unfortunately doesn’t always appear on today’s maps. He writes: “The information which has served to draw up the map has been extracted from the works of M.M. Thiers, of Ségur, of Fezensac, of Chambray and the unpublished diary of Jacob, pharmacist of the army since October 28th.”
Minard even inserts some of his design decisions: “In order to better judge with the eye the diminution of the army, I have assumed that the troops of Prince Jérome and Marshal Davout, who had been detached at Minsk and Mahilyow (today Mogilev) and had rejoined (Napoleon) around Orsha (Orscha) and Vitebsk (Vitsyebsk), had always marched with the army.” This decision certainly must have contributed to Tufte’s admiration: “Graphic elegance is often found in simplicity of design and complexity of data” (Tufte 1983, p. 177). Simplicity may bring elegance but, it also sometimes means that information has been sacrificed. Sometimes, a complex design cannot be avoided, however. Today’s digital environment allows for visualization strategies that help to overcome a reader’s difficulties. A scale bar in the lower right of the map, indicating the map scale, completes the legend (the map measures distance based on the French league, which equals approximately 4 kilometers).
Figure 2-2. A translated and redrawn version of Minard’s map of the French invasion of Russia in 1812. At the top of the map, below the title, a body of text explains the data and symbols used. The orange line shows the path of the army’s march to Moskva, while a gray one tracks their retreat. Below, a red diagram links to the gray path in order to relate temperature to the events of Napoleon’s retreat. Blue marks the rivers, which perform a geographic function in the flow map, and black the place names.
The third step calls on readers to interpret the map itself. As with any thematic map, some basic topographic information is required to orient the theme in space. Here, rivers and place names provide the geographic parameters: Along the western edge is the Neman River, where Napoleon’s campaign began and ended; along the eastern edge, the Moskva River in the east; in the center is the Berezina River, which played a prominent role in the Grand Army’s retreat. East of the Berezina, the map displays but does not label the Dnjepr River. It provides about twenty toponyms—among them Kaunas in the west, Moskva in the east, and Minsk and Smolensk in the center—but adds no symbol to plot their location, leaving their exact location vague. For the map’s theme, Minard reserved the flow lines, inscribing absolute numbers at selected places along the line in order to reinforce the size of Napoleon’s army represented in the flow line.
Time performs an intrinsic function in flow maps, although exact time references rarely occur. Only the diagram at the bottom of the map indicates the time factor in Napoleon’s retreat. It also denotes temperature and links it to both date and location. A quick glance at the study can show, for example, that Napoleon’s army crossed the Berezina River on November 28, when the temperature measured minus 20 degrees Réaumours, equivalent to minus 25 degrees Celsius.
Napoleon crossed the River Neman into Russia with 422,000 troops, and crossed it back into Poland with only 10,000. The flow map expresses this disastrous outcome very clearly. However, it does not explain why the disaster occurred. The temperature diagram tempts readers to conclude that the cold created the calamity. Many paintings of the campaign support this, with their stark depictions of soldiers succumbing to the harsh winter weather (see, for instance, chapter 3, figure 3-1). However, scrutiny of the map reveals that the largest drop in troop numbers occurred on the march toward Moskva, which took place during autumn. Did battle, desertion, or illness cause these losses (Talty 2009)? The map does not indicate the most important battles so it is hard to answer this question. Chapter 6, which describes analytical mapping tools, deals with these kinds of questions in greater depth.
Minard lived in a time when people “invented” many statistical graphics
