By SANDRA RENDGEN
In the world of data visualisation there are only few works which are as universally celebrated as this 19th century statistical map about Napoleon’s Russian campaign of 1812. During this desastrous military endeavour a French army of 420,000 men was almost completely annihilated, only some ten thousand soldiers survived the catastrophe.
The campaign, along with several other gruesome events during the Napoleonic wars in Europe, left a deep trauma in the collective European memory. The map was created in 1869, more than fifty years later by the French engineer Charles-Joseph Minard. Although he had not formed part of the campaign itself, he had witnessed the Napoleonic era as a young man.
Minard is a real champion in the history of data visualisation – no other single person throughout the 19th century has contributed as many elaborate works to the emerging field of statistical graphics. Following his retirement as a civil engineer in 1851, he embarked on a quest to create compelling visualizations to help analysing statistical results, mostly in relation to traffic and trade. Over a period of nearly twenty years (from the age of seventy until his death at eighty-nine years old), he created a comprehensive oeuvre of some sixty statistical maps and diagrams, of which the Napoleon map is the last and most prominent peak.
Napoleon’s Russian campaign began in June 1812 and lasted several months. Countless different army units from various parts of Europe marched towards Moscow, often interrupted by battles, overnight stays, and advances or retreats. In the fall, after the decisive battle which Napoleon had expected in Moscow didn’t happen as the Russians had evacuated the city, Napoleon ordered his men to retreat westwards. Without any infrastructure and support, the army was exposed defenceless to an accelerated onset of winter and the chasing Russian troops.
Minard summarized this succession of events by calculating the decreasing total number of soldiers and visualising it in a flow map – a method which he had elaborated in many different maps before. The flow map is further enhanced by a temperature diagram along the bottom, which is connected to the black flow back from Moscow and adds information about the weather during the retreat.
It is less well known that this work forms part of a comparison. A second flow map on the same sheet visualises the successive losses in men which the army of Carthagian leader Hannibal suffered when approaching Rome across the Alps in 218 BC. Minard constructed both flows to the same scale, making them directly comparable (both flows represent ten thousand men per each millimeter of width). Juxtaposed to the Napoleonic desaster, Hannibal’s 90,000 men may seem like a small army corps. Already before approaching the Alps, however, he, too, had lost some 48,000 soldiers -in battles against local tribes or when crossing natural barriers such as rivers or mountains. Following both flows along their paths and adding the numbers of lives lost along each section is a gruesome reading on the cruelties of war.
This double map is the result of a brilliant conceptual transfer. In his earlier work, Minard had created dozens of flow maps which compared quantities of passengers or goods travelling along particular routes. For the first time in this map, he applied the method to a topic of military history. The rhetorical power of this map is in its focus on one, particularly telling statistical variable: the sharp and steady decline of men in the flow. It is this clear narrative focus which makes this map so powerful in telling a story about the gruesome effects of war.
All images from the archive of the École nationale des ponts et chaussées. Their full digital archive showing the work of Charles-Joseph Minard can be found here.
Sandra Rendgen is the author of two bestselling books on data visualisation and infographics, both published by Taschen. Currently she is getting lost in the history of data visualisation. Her new book about the work of Charles-Joseph Minard will be available in the fall 2018 from Princeton Architectural Press.