Sieges and Fortifications
by Gerald Harris
©1999

Defensive Points
Each structure has defensive points equal to its armor value (AV) times the number of two-meter grid squares it covers (on the ground floor) times the number of stories (each story being 4 meters) the building has.

Attack Value
The attack value of a weapon is based upon its final penetration (for large-caliber weapons, this is the listed penetration at that range plus 2D6). The attack value may be modified by circumstances.

Hit Procedures
When firing at a structure, all normal direct or indirect fire modifiers apply. When the structure is hit, first compare the final penetration of the weapon to the armor value of the structure.

• If the penetration is greater than the actual armor value, use the weapon’s final penetration as the attack value. In addition, items and personnel within the structure take damage. Personnel damage, in D6, is equal to the damage value of the weapon minus the armor value of the structure. Divide this damage among all the personnel within the structure.

For example, a tank fires at a group of infantrymen holed up in a brick farm house. The armor value of the farm house is 3, the final penetration of the tank’s round is 117 and its damage value is 26. The group of infantrymen takes 23D6 (26 – 3) damage, evenly distributed among the personnel.

• If the final penetration is less than the armor value of the structure, but greater than half the armor value of the structure, use one half of the final penetration as the attack value.

For example, an artillery round with a final penetration of 45 hits a bunker with an actual armor value of 50 and 300 defensive points. The final penetration is greater than half the actual armor value of the structure, so the weapon’s attack value is 23 (45 ÷ 2 = 22.5, rounded to 23).

• If the final penetration of the weapon is less than half the armor value of the structure, the attack value is 1. If the firing weapon is a small arm (rifle, pistol, or autogun of less than 20mm bore), roll 1D20. On a roll of 1, the weapon has an attack value of 1, otherwise it has an attack value of 0.

For example, a catapult with a penetration of 0 has an attack value of 1.

When a hit is achieved, subtract the attack value of the weapon from the defensive points of the structure. This is cumulative. Once a structure is reduced to half it’s defensive points, it collapses. All personnel atop or within the structure when it collapses take 1D6 hits, each doing 1D6 damage, are trapped and must be extricated by other personnel. Extricating a trapped individual is a Formidable: Strength task during which no other actions may be taken.

Even when a structure collapses, sufficient external walls and rubble remain to shield defenders. The armor value of this rubble is only half that of the original structure, though. When a structure’s defensive points are reduced to 0, even this protective rubble has been pounded away.

Repairing Damage
Defenders may attempt to repair damage to a structure by shoring, patching holes, or filling gaps with rubble. The difficulty level to restore one defensive point to a structure is a Difficult: Combat Engineer task for three individuals (only one of which needs the Combat Engineer skill), a Formidable task for two individuals, and an Impossible task for one. No other actions may be taken by defenders who are repairing damage. A success indicates one defensive point has been restored. An outstanding task indicates 1D6+1 defensive points have been restored.

Fire
Whenever an explosive or incendiary round strikes a structure, roll 1D6 (+1 if the round was incendiary) on a roll of 6, the structure catches fire. The final penetration of the weapon, minus the armor value of the structure, is the initial level of the fire. The fire will increase in level by 1 every turn (5 seconds) for wooden structures, and 1 level per minute (12 turns) for other structures. Individuals may attempt to put out a fire by spending a turn fighting it. Extinguishing a fire is a Difficult task versus Constitution. For every successful task roll made by an individual, the fire is reduced in level by 1. Outstanding success reduces the fire by two levels. Catastrophic failure results in a burn injury.

If the level of fire exceeds one-tenth of the structure’s original defensive points, the fire will begin burning out of control and cannot be extinguished. At that point, the fire may spread to other structures. If any other structure is within 10 meters of the burning structure, roll 1D6 per minute (12 turns). On a roll of 1, the neighboring structure catches fire with an initial fire level of 1.

An out of control fire will continue to burn until the structure’s defensive points are reduced to 0 (remember, the structure still collapses when half its defensive points are taken). Once the defensive points are reduced to 0, the fire will begin burning itself out. Reduce the fire level by 1 each turn until the fire burns out. During this period, the fire is still a threat to surrounding structures.

Explosive Rounds
Explosive rounds (HE and HEAP) cause structural damage via blast effects. Reduce the defensive points of a structure by the concussion value of the round at that range (i.e., the full concussion value if the structure is in the same 10-meter square as the exploding round, ½ the concussion value if one square away, etc.).

Sample Structures
The following are sample structures from various sources, including Dungeons & Dragons (in case you have any old castle plans lying around you’d like to use), Twilight: 2000, A Soldier’s Companion, etc.

*This is an arbitrary measure equal to 400 times the structure’s defensive points . It works out rather nicely, don’t you think?

¹This is for a 30-meter section of wall. For really big structures like this, it may be easier to break them down into smaller sections. For example, the curtain wall above could be broken down into three 10-meter sections, each with 675 defensive points.

 Construction Times
Sometimes, characters will want to build their own structures. Price wise, use the prices listed above. For construction time, figure one month for every 100 defensive points (so a townhouse with 200 defensive points would take two months to build and cost 80,000).