Mining (TCG)

Note: This chapter refers to rules and concepts used in TSR'S BATTLESYSTEM™️ miniatures rules. Since siege warfare is, by its very nature, an activity involving scores, hundreds or even thousands of troops. BATTLESYSTEM™️ is the system of choice. Of course, this doesn't mean that small segments of a siege can't be roleplayed to great effect using standard AD&D® rules.
__TOC__
==Mining==
If cannon or other methods are unable to breach a castle's wall, the attackers have at least one other option: mining. In simplest terms, this involves digging under the walls of the castle and excavating a "gallery", the roof of which is shored up with posts and wooden supports. When the gallery is large enough, the miners burn out the supports or blow them up, using gunpowder which (hopefully) causes the gallery, and the wall above it, to collapse. The practicality of this technique depends heavily on the type of ground the castle is built on. Soft stone or earth are ideal, since they're (relatively) easy to excavate and solid enough that the gallery won't collapse prematurely. Hard rock is a problem. simply because excavation will be so time-consuming. Sand is perhaps the worst of all, since it's almost impossible to dig out a gallery at all (of course, most castles won't be built on sand). Theoretically, as with digging trenches, any infantry unit can assist in excavation. In practice, however, the troops involved can wear no armor (heavy digging isn't possible while wearing armor) and can carry weapons no larger than short swords. Thus, while a heavy infantry unit might be assigned to mining duty, while they're actually digging their AR drops to 9, and their AD to 6 (representing no armor and only personal weapons).
The speed of excavation depends both on the nature of the ground and on the race of miners involved. This is shown in the following table which lists the volume of earth (in cubic feet) which can be mined in an eight hour shift.
Race of Miner 	Earth	SoftStone	HardStone
Gnoll, hafling, or human	150 	100 	50
Gnome or kobold 	160 	120 	60
Goblin or are 	170 	130 	60
Dwarf or hobgoblin 	180 	140 	70
Ogre 	300 	200 	100
Hill glanl 	500 	300 	150
Fire or frost giant 	600 	400 	200
Stone giant 	1,000	700 	350
In general, only one figure can work in a tunnel; more can work in a large gallery, limited by the actual space taken up by the figures and bases. Thus, three figures of dwarven workers (representing 30 dwarves) digging a large gallery in hard rock could excavate a volume about eight feet high by five feet wide by five feet long in eight hours. Obviously, mining is a slow process, made even slower by the necessity of shoring up the ceiling with wooden supports.
Excavation is gruelling work. Troops can work no longer than eight consecutive hours. After that, they must rest another eight interrupted hours before they can resume digging. There's no reason why troops can't work in shifts, of course.
===Collapsing the Mine===
Once the gallery has been excavated, the next step is to burn out the wooden supports so that the roof and theoretically the wall above-collapses. Usually the wooden supports are splashed with oil, and flammable materials are packed around them. One fig. ure equipped with torches can ig nite the supports; alternatively, spells like fireball can be used. The supports will take 1d3 turns to burn away.
Miners can also use gunpowder to assist the burning of the supports (historically, the Spaniards used this technique). Unless gunpowder is confined, it doesn't explode. Even so, however, bags of gunpowder piled around the supports burn very rapidly and improve the chances of collapsing the gallery.
Whether or not gunpowder is used, mining is never one hundred percent sure. This is reflected in the following table. When the attacker attempts to collapse the gallery, roll 1d10:
DieRoll 	Result
1-2 Supports fail to burn away; no effect 	
3
Supports burn but gallery fails to collapse: no effect 	
4-5 Gallery collapses, but with no damage to structures above; no effect	
6-10 Gallery collapses full effect on structures above 	
Note: Add +1 bonus to die roll if gunpowder is used.
If a mine fails to collapse, the miners must enlarge the gallery by 25% of its current volume before trying again.
===Mining Damage===
The amount of damage inflicted on structures above by a collaps. ing mine depends on the volume of the gallery and the terrain on which the castle stands. A collapsing gallery inflicts the following number of hits for each 1,000 cubic feet of gallery volume:
Earth 	2d8
Soft Earth	1d8
Hard Stone	1d6
For example, a castle is built on soft stone. The attackers have excavated a gallery 20 feet wide by 30 feet long by 10 feet high (6,000 cubic feet) beneath one of the walls. If the gallery is successfully collapsed, it will inflict 6d8 hits on the wall above.
Explosive Gunpowder Mines Sometimes conditions can be arranged so that the gunpowder used in a mine actually explodes. Perhaps the gunpowder is packed tightly in earthenware containers or something similar.
The most spectacular use of a gunpowder mine was at the fall of the French castle of Uovo, near Naples, in 1503. The castle was situ ated on a narrow peninsula separated from the mainland by a deep ditch, and cannon alone were powerless to reduce the place. The attacking Spaniards had an expert among them-Pedro Navarrowho had perfected the gunpowder mine. After spending three weeks digging a large enough gallery. Navarro packed it with gunpowder and touched it off. The powder exploded spectacularly, blowing much of the wall into the air, and killing the castle's governor and his council who were at debate in the chapel above the gallery. The amount of damage done by gunpowder depends on amount used. The base damage done to structures above the gallery is shown in the following table. The figures represent the number of hits inflicted for each 100 pounds of gunpowder used:
Earth 	1d6
Soft Stone	1d4
Hard Stone	1d3
These hits are in addition to those inflicted by the collapse of the gallery (see the table in the section on "Mining Damage").
Getting gunpowder to explode is always problematical. This is reflected in the following table. When the gunpowder is touched off, roll 1d6.
DieRoll 	Result
1-2 Gunpowder burns, but does not explode. Use the table in the section "Collapsing the Gallery". 	
3-4 Gunpowder "flares up" (minor explosion). Gallery collapses, and the explosion does one-half damage (in addition to the damage inflicted by the collapse of the gallery).	
5-6 Gunpowder explodes, collapsing the gallery and doing and doing full damage (in addition to the damage inflicted by the collapse of the gallery). 	
Note that the above tables are used only if suitable preparations are made to cause the gunpowder to explode, not simply burn.
===Battles in the Tunnels===
If the defenders know that mining is going on, there's no reason why they have to simply sit still while the attackers go about their business. Historically, countermining was not an uncommon tactic.
Once the garrison has established the location of the enemy mine (by observation, listening, or magical means), they might begin excavations of their own. The garrison would dig a tunnel that met up with the enemy's gallery, then send troops down it to kill the attacking miners. The weapon and armor restrictions on miners applies to both sides... at least while excavation is actually going on. Once tunnels are complete, however, fully-armed troops can be sent down them, limited only by the space in the excavations.
Counter-mining was raised to an art by the Muscovites when Moscow was besieged by the boyars in 1606. The Muscovite miners had prepared secret galleries under the walls, and from there, they dug under the foundations and out. They located the attacking mines and galleries, broke into them and killed the enemy miners. In some cases, they even excavated under the attacking galleries and blew them up with gunpowder.
Rules for morale and movement in tunnels are identical to those referring to buildings, with the following exceptions. Missile combat (except for spells such as magic missile) is forbidden; there is simply not enough space to use such weapons effectively. If figures representing unarmored and lightly-armed miners are met by fully-armed troops, all Morale Checks made by the miners are at -2.
For movement purposes, tunnels are considered as rough/rocky terrain. Troops in tunnels and galleries can be ordered to "hold the breach".