MCRP 12-10B.1, page 52

position is often behind or inside the last large building before crossing the LD. The LD should be located on the near side of an open area running perpendicular to the direction of attack, such as a street or rail line. (5) Time of Attack. Ideally, the time of attack should be conducted during hours of darkness or limited visibility. Marines can exploit the poor visibility to cross open areas, to gain access to rooftops, to infiltrate enemy areas, and to gain a foothold. When attacking in unrestricted visibility, units should use smoke to conceal movement. (6) Reserve. Reserves should be mobile and usually follow in trace of forward units. Battalion reserves normally follow one to two blocks to the rear of the lead company. If a company reserve is available, it follows within the same block so that it can immediately influence the attack. A unit with a reserve mission can be called upon to: Exploit an enemy weakness or friendly success Attack from another direction Attrit and/or clear bypassed enemy positions (normally requires designation of a new reserve) Secure the rear or a flank Maintain contact with adjacent units Counterattack (7) Security. Each unit should ensure security of its flanks and rear (Figure 2-8 on page 2-20). Fighting in a built-up area is unique in that attacks can come from all three dimensions. Units assigned a mission to isolate can also provide security. Small units conduct security patrols and guard OPs to supplement higher level reconnaissance and security operations. (8) Engineers. Leading units should have engineers attached for immediate support. Tasks commonly assigned to engineers include: Preparing and using explosives to breach walls and obstacles Finding and exploding mines in place or helping to remove them Military Operations on Urbanized Terrain 2-21