Countermining

Tunnel warfare is a general name for war being conducted in tunnels and other underground cavities. It often includes the construction of underground facilities (mining or undermining) in order to attack or for defence and the use of existing natural caves and artificial underground facilities (catacombs, city communications, etc.) for military purposes. Tunnels can be used to undermine fortifications and slip into territory, while it can strengthen a defence by creating the possibility of ambush, counterattack and the ability to transfer troops from one portion of the battleground to another unseen and protected. Also, tunnels can serve as shelter for combatants and non-combatants from enemy attack.

It has been used since antiquity against a walled city, fortress, castle or other strongly held and fortified military position. A counter mine is a mine dug to allow defenders to attack miners, or destroy a mine threatening their fortifications. It can be sometimes linked with urban warfare, as tunnels are often found in urban areas and cities, although urban warfare as a whole usually dominates any tunnel considerations.

Tunnels, due to their nature, restrict fields of fire and thus any troops in a tunnel usually only have a few areas exposed to fire or sight at any one particular time. They can also be part of an extensive labyrinth and have cul-de-sacs as well as reduced lighting that can create a closed-in night environment.

The Greek historian Polybius, in his Histories, gives a graphic account of mining and counter mining at the Roman siege of Ambracia:

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