Tuesday, January 10, 2012

Making the Most of the Place

The exact siting of a fortified work (which isn’t always a castle as a residence) depends on finding the most defensible terrain upon which to build the works that fits the mission.

Works designed to protect something (the cookie jar is behind you) such as towns, ports, towns or even cities have to find a ring of defensible positions around the entire location.  The choice of sites has to compete with the best place to defend versus the limits of materials.   This is also true of major works such as the Great Wall of China and the Roman Limes that were built across northern Britain and from the Mouth of the Rhine to the Danube. 

 But at this junction we will look at the components of a fortified work that go into any of the works be they behind or before the cookie jar or actually have it.    Consequently a glance at a topographic map to check out the major ridges and river reveal the logic behind the locations of cookie jars, and the military aspects thereof.

Flat or Not Flat. Wet or Dry?

There are two basic choices in siting the fortification: the ground is flat or it is not.  And when it is flat, is it wet.   The engineer then will reinforce the slope and angle of the existing terrain, built high ground from scratch, or dig a moat filled with water too wide to jump across and deep enough to drown those who try. 
Killing Zone, the last one hundred meters
The deadliest part of an assault on a position, fortified or not, is the last one hundred meter.  That is where hand and eye coordination of a weapon of sufficient accuracy or volume makes it a killing zone.   Crew served weapons of those days could put deadly fire out to three to five hundred meters away. 

The coordination of interlocking grazing and plunging fires is built into the walls of the fortification to make sure that multiple weapons cover the same square foot in front of, on top of, and behind the walls.  We call this a beaten zone.

Grazing fires occur at relatively shorter ranges and are used to sweep corridors, the face of the walls and towers, which fires plunge into the upright walls and turrets against those scaling the walls.
Taking advantage of the natural slopes for the construction of walls and towers, we can use the Handy approach:

The actual selection of site is favored by clear fields of fire and observation down the slopes of the high ground and of the fortifications themselves.

In the diagram above, the choices of the fortress engineer is to make sure there is no dead space for besiegers to take cover behind.  The engineer typically will move the walls and towers of the fort at locations C forward until the dead space is observable.

In this case of Chateau Gaillard, the towers have been placed to provide maximum fires whose plunge grazes the slopes to places even in defilade.  Stonewall Jackson, Confederate General at First Bull Run positioned his riflemen on Henry House Hill to have the same effect; his troops were in defilade position from chest down, but their bullets hit Union troops out of line of sight.

In these cases, the fortifications are built on high ground which not only affords better observation and fields of fire, it makes it difficult to attack the walls and towers of the fortification itself by denying access to the base of the works.   

Cross Fires

In addition to having plunging fires that graze through the ranks of those who dare to climb, fires are placed to provide mutual support to adjacent walls, towers, and gates.  When walking through a fortification, look for how many arrow slits and other interesting openings can fire upon you.  It’s rare not to find at least three.

These placements on the Great Wall are within mutual arrow distance apart and have a 360 field of observation and fires on both sides of the ridge line upon which most of the Great Wall was built.
The distance between towers is based on risk assessment in view of the maximum effective range of the missile weapons at hand.  The maximum effective range today is measured by the distance a standing person can be hit.  In those days, most missiles, arrows, rocks, and boiling oil were addressed “to whom it may concern” and given that battle formations were shoulder to shoulder, or at least arm’s length, it concerned a great many.  One hundred yards was close combat with indirect and supporting fires from as far as five hundred meters for the really big stuff.  Three hundred yards is “in range”. 

cross fire.In the case of Carcassonne you see defense in depth, with a wall with no protection on it’s back side, in case the enemy took the first set of walls, they would be in a deadly cross fires. 

The art and science of fortifications in the following gunpowder days as was the art of sieges highly sophisticated as the range and lethality of cannon grew.  Some of the features found in Templar days continued well into the age of Exploration as in the case of the Fortress San Juan de Ullua in Vera Cruz, Mexico where arrow slits coexisted with cannon ports.

Firearms also modified the basic structure of fortifications from > to < looking to the right.  Archers normally fired through an arrow slit narrow on the outside for protection. Firearms because of their weight and discharge of smelly smoke had to be outside the walls and fired from a widening aperture to allow swiveling the guns.  Some forts had their arrow slits widened for guns, which later became windows.  If it looks like a window, it wasn’t built that way.

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