Previous: 2-51: Urban Terrain
2-53. In cities, subterranean features include underground garages, passages, subway lines, utility tunnels, sewers, and storm drains. Most allow troop movement. In smaller towns, sewers and storm drains may permit Soldiers to move beneath the fighting to surface behind the enemy. Knowledge of nature and location of underground facilities is of great value to both the urban attacker and defender. Subterranean routes can grant attackers use of both surface and subterranean avenues of approach, enabling them to place a smaller force behind enemy defenses. Depending upon strength and depth of the aboveground defense, attackers along the subterranean avenue of approach can become the main attack. If subterranean efforts are not immediately successful, it forces defenders to fight on two levels and to extend his resources to more than just street-level fighting. (Refer to ATTP 3-06.11 for more information).
2-54. The presence of subterranean passages forces defenders to cover urban areas above and below ground with observation and fire. Subterranean passages are more a disadvantage to defenders than the attackers are. However, given the confining, dark environment of these passages, they do offer some advantages when thoroughly reconnoitered and controlled by the defender. A small group of determined Soldiers in a prepared defensive position can defeat a numerically superior force. Subterranean passages—
- Provide covered and concealed routes to move reinforcements or to launch counterattacks.
- Can be used as lines of communications, for movement of supplies, evacuation of casualties, and to cache supplies for forward companies.
- Offer defenders a ready-made conduit for communications wire, protecting it from tracked vehicles and indirect fires.
- Afford attackers little cover and concealment other than darkness and any manmade barriers.