1. Clearing Stairwells and Staircases - Stairwells and staircases are comparable to doorways because they create a "fatal funnel." The danger is intensified by the three-dimensional aspect of additional landings. The ability of units to conduct the movement depends upon which direction they are traveling and the layout of the stairs. Regardless, the clearing technique follows a basic format:
• The leader designates an assault element to clear the stairs.
• The unit maintains 360-degree, three-dimensional security in the vicinity of the stairs.
• The leader then directs the assault element to locate, mark, bypass, and or clear any obstacles or booby traps that may be blocking access to the stairs.
• The assault element moves up (or down) the stairway by using either the two-, three-, or four-man flow technique, providing overwatch up and down the stairs while moving. The three-man variation is preferred (Figure 7-15).
a. Units must guard all avenues of approach leading into their area. These may include—
• Enemy mouseholes between adjacent buildings.
• Covered routes to the building.
• Underground routes into the basement.
• Approaches over adjoining roofs or from window to window.
b. Units that performed missions as assault elements should be prepared to assume an overwatch mission and to support another assault element. To continue the mission--
• Momentum must be maintained. This is a critical factor in clearing operations. The enemy cannot be allowed to move to its next set of prepared positions or to prepare new positions.
• The support element pushes replacements, ammunition, and supplies forward to the assault element.
• Casualties must be evacuated and replaced.
• Security for cleared areas must be established IAW the OPORD or TSOP (Tactical Standing Operating Procedure).
• All cleared areas and rooms must be marked IAW unit SOP.
• The support element must displace forward to ensure that it is in place to provide support (such as isolation of the new objective) to the assault element.