Sunday, April 21, 2013

It's More Than Just Grass

My next post about DH Hill will cover the battle of South Mountain. After that post, it will be time to explore Hill at Antietam, which is great because it will give me an excuse to ramble on and on and on about my very favorite thing---TERRAIN!!!!!!!!! Lucky for me, Hill's Division was all over the field so I will be able to blend and examine the two, Hill and Terrain, together. In addition, I plan on introducing a few cartographers and topographers that were present at Antietam and shed some light on their contributions. In the meantime, I figured I'd give a synopsis on the science of Civil War cartography and topography.
Recon of ground made by Hooker's 1st Corps. Map made by DC Houston, WA Roebling, WS Long.

Topography is the geography of regions or localities considered collectively and in detail. Physical features are NATURAL and divided into relief, that of land and its elevation, and drainage, that of water.  The artificial features made by man are referred to as CULTURAL and added to the natural features for a complete picture of terrain. Terrain is the limited part of land surface on which tactical and strategical operations occur. The description and delineation of terrain and how it affects operations is called military topography. To see what “effect terrain will have on tactical should be broken down into its natural units, such as a valley, a range of hills, plain or forested area. Analyze each unit to see what effect it will have from both friendly and enemy viewpoints. This analysis should specifically cover concealment, avenues of approach, lines of communication, natural and artificial obstacles, observation and fields of fire for all weapons.”(1)
The job of the Civil War military topographer was to explore and report on a region assigned to him. He had to learn the physical features of the terrain (relief and drainage) and identify and mark the cultural features of the landscape (man made). The combination of the two formed the army’s environment.

Topography is divided into map reading, topographic sketching, and surveying. For those planning and/or conducting operations, it was essential to have mastered these skills because the time to be worrying about the map was BEFORE the battle, not during or after it.  Since one cannot predict what will happen in active operations, it was better to prepare for every contingency and nothing screamed “prepared” like a  map. However, a map IS an accurate representation of the terrain made with precision instruments. At Antietam, any “maps’ would have been handmade topographic sketches, providing an approximate representation of the terrain. The sketches took the place of nonexistent maps or supplemented the few that existed. Sketches were either of an area or route, and both were categorized as reconnaissance. Area sketches provided specialized information such as enemy camps, terrain features along an outpost line, or a military situation at a given time within a specified area. Route sketches displayed all natural and military features on and in the immediate vicinity of the route passed over or to be taken, such as houses, bridges, and vegetation.(2)
Drawing Instruments
The first step in creating a map was measuring distance. There were numerous ways to calculate distance and more popular options included estimation, pacing, triangulation, wheel revolutions, and time. The rope and chain method was used to mark and count small distances. Longer distances were either estimated or paced. For a topographer with average eyesight the following could be estimated with little error---"9-12 miles, church spires; 5-7 miles, windmills; 2-2.5 miles, chimneys; 2000 yards, trunks of large trees; 600 yards, individuals of a column; 500 yards, individual panes of glass in windows; 400 yards, arms and legs of dismounted men." ***Note to yourself---remember 600 and 400 yards, an illustration of this will be shown in a later post***. However, the estimation method was affected by weather, “objects appear to be nearer than they really are when the sun is behind the observer and the object is in a bright light...objects appear to be farther away than they really are when they are up a steep hill from the observer...and when seen across undulating ground.”(3)
Transit- measures elevation

Wye Level-establishes land contours

After interpreting the terrain, the second part of making the map was representing the survey data in its correct positions and providing a clear picture of the terrain. Based on what information a commander wanted, the data was plotted in such a way that when considered, all relevant pieces were available for examination and a tactical operation could be planned and executed. A good military map had to be accurate, legible (even in poor light), easily understood with conventional symbols, and made on durable paper. In addition, the map was named, dated (to show field work, issue, or revision), and scaled. Each map was drawn at least twice, first in pencil to correct any errors and then in ink for the commander. The drawing board had to be kept dry so as not to ruin the ink drawing. The topographer had to determine which parts of the map he would draw first---if he was right-handed he would start in the upper left corner and work diagonally to the lower right to keep his hand ahead of wet ink thereby avoiding smudges.(4)
Aneroid Barometer- measures differences in elevation

The satisfied feeling that came from completing a map was not one the topographer usually got to often enjoy. As soon as the ink dried, the map needed updating. In active military operations the situation was fluid. On the battlefield, a field may be rendered impassable for artillery wagons due to heavy artillery fire or a retreat route may be threatened due to a damaged bridge, a lush forest levelled,  and fortifications or earthworks built/destroyed. Armies traipsing across the land altered every piece of landscape they came in contact with. What once was may no longer be and thus maps needed to reflect the most current information in order to prepare and execute operations.

In regards to terrain, Antietam was full of concealment (hill, ridge, woods, river bank, town), compartments (depression, ravine, sunken lane), obstacles (steep hill, deep ravine, stream), observation points (hill, woods), fields of fire (flat field), and key points (critical natural and cultural features)  that impacted tactical operations.
---Concealment hides men and/or equipment while also taking into consideration the changing appearance of terrain due to the time of day, weather, and season. Not all areas of concealment can be represented on a map due to the terrain's depth. Nonetheless, it is imperative to identify areas of concealment and surmise what could be placed in these areas, by both friendly and enemy forces.
---A compartment is terrain that is high enough to screen from direct fire or observation. Typically, an area of low ground, such as a depression, is enclosed by high ground, such as a rise or hill, and acts as a pocket of security. If a compartment is long and narrow and leads into/behind enemy lines then it is a corridor. If this corridor is situated behind the main line then it is a cross compartment as it funnels men to and fro. Compartments can have one or several exit/entrances. Piper Farm is an excellent example of a terrain compartment (and I can't wait to dive into that!!!). A topographer should have identified areas of concealment and compartment on a map so that a commander could identify what areas needed to be held/taken in order to facilitate troop movements while thwarting enemy movements.
---Obstacles are terrain features which hinder movements and can be natural or cultural. At times, and if used properly, an obstacle can be an asset used against the enemy. Therefore, it is imperative to analyze how an obstacle influences any movements.
---Observation points are located on higher ground BUT not on the crest of a ridge/hill. The function of an observation point is to examine the terrain from friendly and enemy viewpoints without the enemy observing in return.  These points can vary from a hill to woods but must offer a line of sight to inspect whether the terrain helps or hinders.
---Fields of fire are flat fields or crests from which infantry/artillery can directly aim at a target. Not all fields of fire are good for both infantry and artillery so it is necessary to stand on the field to assess the range and then decide on the proper weapon.
---Key points are simply that, a prominent terrain feature that if possessed determines the outcome of the operation. Key points can be natural or cultural.(5)
So that's terrain in a nutshell. From here on out, I will be examining a plethora of locations at Antietam. Each location will be assigned to one (or more) of the above categories and its impact on operations will be explored. 
Piper Farm Compartment

1. Technique of the Terrain; Maps and Their Use in the Field of Peace and War by HA Musham. 1944, pg 171.
2 Musham pg 7-8, 11-12.
3. Musham pg 95.
4. Musham pg 165-166, 169.
5. Musham pg 171-173.

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