Inspirational: Battle Maps

My inspirational data visualization isn’t a single specific work, but rather a more general type of data visualization.

Public domain work by Hal Jespersen (http://posix.com/CWmaps/)

Battle maps are something anyone who has read about war has seen. They illustrate the movements and interactions of different belligerents during armed conflicts. Details will vary from artist to artist, but all battle maps start with an actual geographic map of the battle location. On top of that, troop movements are represented. In this example, Hal Jespersen uses thick colored lines to represent various sub-orginizations of soldiers holding a position. Emanating from those are arrows, indicating advancement. Occasionally, an arrow with a dotted line is shown indicating retreat. Names are written near standing soldiers indicating the commanding officer’s name and serving to identify that group.

What I find fascinating about these maps is how they tell a story that can take place over days and weeks in a single static image. The entire story of rest, advancement, battle, defeat and retreat is told without varying time at all. Towards the bottom we can see, for example, that Toombs was holding the position behind the river, but was overrun by Burnside’s offensive across the bridge and forced to retreat. In response, A.P. Hill (arriving later) was sent to cover Toombs’s retreat and counter the advancing enemy. Burnside’s troops engage D.R. Jones’s forces to the North. The goal of the blue forces is to reach the city of Sharpsburg which is cocooned in thick red lines defending it.

Other stories are evident in the map as well. Several of sumner’s advances were forced to retreat, with D.H. Hill’s forces holding their ground. However, these forces were themselves forced to retreat and be reenforced, only stopping Sumner when they had pulled back considerably. This back and forth swing of domination of the battle field implies a very violent conflict, and the area is labeled “Bloody Lane”.

Battle maps are not perfect, and this example of their design is certainly no exception. In larger maps, it can become difficult to discern the chronology of events. In the example given, it is also impossible to tell the scale of the timeline in question. Did this battle take place in an hour? A day? A week? Anyone of them is a plausible answer, and the map does little to address the issue. The only hint we are given is the fact that A.P. Hill arrived in the “late afternoon”. The battle would have to have happened over the course of less than a day for that label to be meaningful.

Like I said, I really like how the events “as they unfold” are depicted statically and rather effectively. Complex narratives can be extracted from the map easily, and the goals and ambitions of two warring groups are made plain to see.