MCRP 12-10B.1, page 87

the terrain limits the enemy’s ability for engagement or if strongly constructed buildings that give defenders protection are available. The mission of such a force is to provide early warning of the enemy’s advance, to engage the enemy at long range, and to deceive the enemy as to the true location of the defense. This force should withdraw in time to avoid decisive engagement. If there is limited observation from the forward edge, a force should be positioned on more favorable terrain to gain better observation and to engage the enemy at long range. Reconnaissance by all defending elements should help select routes for use by defenders moving between positions. Movement is crucial in fighting in built-up areas. Early selection and marking of routes adds to the defender’s advantages. The commander covers probable landing and drop zones such as parks, stadiums, or large rooftops and heliports with obstacles or fire to prevent air assault. (See Appendix F.) In a large built-up area, a unit is given a sector to defend and normally establishes a series of defensive positions. Although mutual support between positions should be maintained, built-up terrain often allows the enemy to infiltrate between positions. Therefore, the defender must identify the following: Positions that allow suppressive fires on infiltrating routes Covered and concealed routes, such as subways and sewers, for friendly forces to use to move between positions Structures that dominate large areas Areas such as parks, boulevards, rivers, highways, and railroads where antiarmor weapons have longer fields of fire Firing positions for mortars Command locations that offer cover, concealment, and ease of command and control Protected storage areas for supplies. Buildings that enhance the general plan of defense are selected. Mutual support between these positions is vital to prevent the attacker from maneuvering and outflanking the defensive position. Buildings chosen for occupation as defensive positions should: Offer good protection Have strong floors to keep the structure from collapsing under the weight of debris MCWP 3-35 .3 3-16