Field Engineer's Guide To Fortifications

The Field Engineer's Guide to Fortifications is a document distributed by the Stormwind Army detailing new developments in the art of fortresses.

=Introduction=

The art of the fortress is much spoken of these days, as it undergoes sweeping changes brought about by the adoption of gunpowder artillery. Much of what previous generations knew about fortresses has been swept aside, and an uneducated engineer is more a liability than an aid in dealing with the new situation.

=The Old Style: Castellan Fortifications=

For hundreds of years, the dominant form of fortress was the castle. Massive, imposing, and reassuringly solid, castellan fortresses are representative of strength in many cultures. However, cannon can easily make a mockery of this strength.

Structure of a Castellan Fort
Castellan architecture is usually tall and imposing. Its height is its primary advantage in combat, making it very difficult to scale and affording defenders a good vantage for shooting.

The outermost layer of defense may include a ditch (often filled with water to form a moat) that serves to obstruct the travel of enemy forces, especially equipment such as siege towers. Between the ditch and the wall is an area of cleared ground called the pomery. Smaller fortifications like town walls lack ditches, relying on the pomery as the perimeter of their defense.

The primary curtain wall is usually at least two or three stories high and is fronted by a steep, stone-clad slope called the talus. The talus makes it harder to assault the base of the wall with siege towers, rams, or sappers. In addition, stone shot dropped upon the talus will shatter, hurling fragments into the attackers.

At the top of the wall is a parapet, a chest-height wall of stone with battlements cut into it. Crenelations or loopholes in the wall allow defenders to shoot at advancing enemies. The parapet often projects out over the top of the wall; gaps in the parapet floor called machicolations allow arrows or other weapons to be used on enemies climbing up the wall.

Towers are built from the curtain wall at points, usually rising at least two additional stories in height. The shape of towers varies; a square tower provides greater internal space for garrisoned troops, whereas a round or octagonal tower is better at resisting the blows of catapults and other siege weapons.

Inside the curtain wall are courtyards surrounded by the essential structures of the fortress such as barracks and warehouses.

Castles are sometimes built as layered fortifications if their position is valuable enough. An additional curtain wall or a solid structure (the keep) with its own towers (called turrets) is built behind the original. Usually this structure is built taller or located on a rise, such that the defenders can fire over the primary wall at enemies.

Defending Castellan Fortresses
Unmodified castles can be quite difficult to defend against a modern army equipped with cannon. The advantage provided by these war machines must be nullified before they can be allowed to present on the walls. Defending cannon can be placed in towers, though they made need to be modified with larger loopholes and more open space to allow smoke and hot gases from firing to dissipate.

Troops should be dispatched to locate and disable the enemy’s artillery as a matter of urgency. Once the enemy arrives at the fortress, assaulting their artillery with infantry or cavalry may be vital. The castle continues to be of use as a stronghold, though; even if battered down by cannon, it must be assaulted by enemy troops, a time-consuming and deadly process.

If feasible, one of the best ways to use a castle is as an "anvil" in a flanking maneuver. An army group outside the fortress maneuvers in such a way as to entrap the enemy between the army and the castle, offering them no escape and denying them the opportunity to reduce the fortification at their leisure.

Reducing Castellan Fortresses
Engage the castle from range with cannons if at all possible. Focus on removing the towers so that they cannot serve as positions for defensive archers or gunnery, then dismantle the walls as much as feasible.

If cannon are not available, assaulting the fortress is a much slower and more dangerous process. Sappers should be deployed to destroy the walls, whether by deploying explosives while the defenders are distracted or mining underneath them.

=The New Style: Modern Fortifications=

Modern fortresses, known as "star forts" for their shape as seen from above, are designed to use earthworks and geometric lines to funnel the enemy into avenues of approach that are well-guarded by cannonfire from the walls. Enemy cannons are hobbled by the fortress’s low profile and are destroyed by counter-battery fire.

Structure of a Star Fort
The outer line of the star fort is a large trench just below the incident terrain called the covert or covered path. This path allows defenders to patrol the grounds in relative safety and covers allied forces moving towards the fortress while preventing an attacker from retreating as easily.

Inward from the covered path is a massive berm, the glacis, that rises above the terrain. The peak of the glacis is just below the top of the curtain wall. It is asymmetrical, with a very broad outward slope and a steep inward slope that is sometimes reinforced by wood planking. The purpose of the glacis is threefold: it prevents enemy cannon from presenting on the base of the wall, it prevents enemy troops from easily storming the fort, and it provides shelter to allied troops moving from one part of the works to another. Trenches are cut through the glacis at an angle to allow soldiers to move in and out of the fortress.

Between the glacis and wall is another trench, the ditch, formed of the dead space between the counterscarp (rear) of the glacis and the scarp (front) of the wall. The ditch is highly vulnerable to cannon and musket fire from the wall and its bastions; no point of the ditch is not in sight of at least one bastion. In a pitched battle, the ditch is the primary killing ground.

Inside the ditch there may be further defenses. Galleries or caponiers give a cover space for infantry to shoot at attackers; their external walls are solid save for loopholes and they connect to the garrison via tunnels under the wall. The former refers to a feature parallel to the ditch, whereas the latter runs across it. Ravelins are a defensive hard point, similar to bastions, that are set in front of the curtain wall and do not connect to it. The ravelin is a strong firing point for troops and cannon, but if it is captured, the remainder of the fortress is not at risk. A tenaille is a small section of wall that is similarly disconnected and protects a vulnerable feature in the main wall, such as a gateway.

The curtain wall is the perimeter of the fortress. It is fronted by a talus, a short, steep-sided earthen mound. The talus hinders enemy troops scaling the wall and provides some structural support. The wall itself is faced with brick for durability, but is filled in with large quantities of dirt to provide protection from cannon fire.

Projecting from the curtain wall at intervals are bastions. Similar in composition to the wall, they are emplaced with cannon which can sweep the length of the ditch around them. Each bastion’s base is covered by fire from the bastions on either side. The ideal shape for a bastion is a diamond with the point further from the wall elongated to ensure no cover for the attackers.

The parapet is a short wall with battlements that is often included atop the curtain wall, bastions, and ravelins. Parapets are constructed from brick to provide protection from musketfire and prevent spalling damage when struck by cannon.

Inside the curtain wall are non-fortified structures: housing, arsenals, workshops, etc. These structures are often built at least partially underground to make better use of the available space. Mustering yards and other open spaces are also provided for in the fort’s plan.

Star forts are often built in layers. Inside the curtain wall, a citadel or stronghold may be formed from a separate curtain wall with its own bastions and other features.

Defending Star Forts
Because of their lower profile, star forts require a more active defense than in past eras. Troops and cannon must be stationed on the walls in advance of the enemy’s attack. Where there are several lines of defense (such as ravelins in front of the curtain wall, or a second set of walls behind the first), troops should be positioned on at least two layers so that fire from the inner defenses covers the retreat of troops from the outer.

Enemy cannon approaching over the glacis represent a significant threat if allowed to reach firing positions. Strong counter-battery fire should be directed to ensure they cannot set up and bombard the fort.

If the enemy enters the defensive perimeter of the fort, there are usually strong opportunities for a counter-attack. The ditch in particular is a constrained area that will limit enemy maneuvering and is vulnerable to shooting from the walls and assault from one or both directions simultaneously. A well-timed counterattack can disrupt the enemy’s advance or even force them from the ground entirely.

Reducing Star Forts
Star forts are designed to be difficult to sap or bombard. Cannon shooting over the glacis must elevate their barrels considerably, reducing range and power, and both cannon and mortars will likely be outranged and outgunned by bastion guns.

However, these advantages apply only as long as the enemy can keep their walls manned and their troops alert. Though costly, a diversionary assault or bombardment can distract the enemy long enough to deploy sappers at a different point on the defense perimeter. If the outer defenses can be disrupted, cannon moving into place atop the glacis can cause severe damage.

The star fort’s reliance on counterattack and active defense can also be used against it. With proper timing and deployment, an enemy force can be lured outside of its walls and destroyed, weakening the defenders considerably. Be alert for any opportunity to draw the enemy beyond the range of gunfire from the wall, where they will lose their primary advantage.

Should time or circumstance dictate a frontal assault, such an attack is likely to be costly. However, it can succeed if the attackers are able to bring enough firepower to bear. Short-range fire from archery, muskets, mortars, or small cannon should be used to suppress defenders on the wall while ladders and grappels set up. A small number of troops may be able to scale the wall and successfully open the gates or, more likely, cause enough of a general disruption for cannon to be brought over the glacis and engage the fortress directly.