MCRP 12-10B.1, page 127

(e) Reducing enemy strongpoints using demolitions and heavy equipment. (f) Preparing helicopter landing zones (HLZs). (g) Assist in the preparation of defensive positions in the event of a counterattack. (2) Defense. An urban area can be made nearly impregnable with proper organization of the battlespace and skillful preparation by engineers. Obstacles in outlying areas can delay/disrupt the enemy and canalize him/her into engagement areas. The streets and alleys inside a city can also be use to canalize enemy forces into engagement areas and kill zones. In preparing the defense of an urban area, engineers perform several critical tasks to include: (a) Engineer preparation of the urban battlespace. This should begin well outside the city with complex obstacles in support of security forces. Selective demolition of bridges and roads and other countermobility measures can force the enemy into taking avenues of approach that favor the defense. (b) Constructing obstacles forward of and between defensive positions to block, disrupt, fix, and turn enemy attacks. A majority of the obstacles will be directed at interfering with the movement of personnel and vehicles, but some effort must be directed at preventing vertical and subterranean movement. Material designed especially for obstacles and barricades, such as barbed wire and tetrahedron(s), is necessary, but improvised barriers can be just as effective and are readily available. Vehicles and building rubble are the most common improvised barriers. (c) Enhancing mobility by opening and/or marking preplanned routes into attack positions for counterattacks or alternate positions to protect a flank. (d) Providing technical advice on which buildings are more suitable for use as strongpoints or which rooftops are strong enough for helicopter landings can be vital. Any reinforcement of building roofs should be supervised by the engineers. (e) Preparing tank positions that offer them cover and concealment. (f) Assisting infantry units in clearing clear fields of fire, especially for longer range weapons like the TOW. (g) Playing a potential role in the maintenance of critical urban services such as power, water, and communications. This function may also be performed by naval construction units. (h) Assisting in the preparation and maintenance of railroads, airfields, and ports. This function may also be performed by naval construction units. MCWP 3-35 .3 4-14