Not all of us have the luxury of a 90mm gun but Ralph's words are worth reflecting on. If you have heavy weapons and the situation permits their use it is often better to "bring the house down" on an enemy rather than risk your own troops' lives house clearing. Better to send a shell or rocket rather than men. As well as tank gun fire infantry anti-tank weapons and direct fire from artillery can be used.
For when such means can't be used, this is an article about entry techniques and room clearing. In other words, how to enter a room of potential hostiles and not come out in a body bag. This is mainly a matter placing yourself in the most advantageous position. First, of course, you have to get into the room, and the access points can either be the doorway, window or a hole in the wall. All have their pros and cons. If the access point already exists and is open, then you can either move in swiftly and quietly or you can storm in. The first way may take the foe unawares and allow you to get into position before they realise it, while the second may benefit you by causing confusion and panic. Military units and SWAT teams can often precede themselves with a stun or concussion grenade but such luxuries may not be available to a homeowner who hears an intruder or to a patrol cop.
If the access route is locked, then other measures must be taken, and a friend wisely notes:-
"'Dynamic access' comes down to one or more of four basic tools:
a one- or two-man battering ram.
the Haligan Tool, an oversize combination of prybar, claw hammer, and pick-ax.
stand-off muzzle devices for shotguns, combined with special ammunition, and
Each has advantages and disadvantages, and none is absolutely fool-proof."
To this list I might add that the Israelis have a rifle-grenade for door breaching. Sledge Hammers and Rams are for doors that open inward; Prybars and Hooligan tools are for those that open outward. This device can handle both types. There are various interesting devices available to a SWAT or Military unit. The Doorbuster appears to be a safer and more effective alternative to the shotgun.
Explosives can be used to create a doorway in a wall, and windows can also be used as an access route - slower to move through but less likely to be boobytrapped.
Whatever the method used to create an opening eventually a team has to go through it.
An important thing to consider is Attitude. The SAS have a little aide to getting this right for CQB:-
S-A-S. Speed, Aggression, Surprise.
There are various ways to clear a room. Even the various US Army Field Manuals on the topic seem to have a slightly different method in each.
One way is for the team to operate by a set routine. Each man is assigned a corner of the room to head for. He clears his corner of any hostiles then engages any other targets in the room. No 1, or the Point man, goes through the door first, and heads to the left nearside corner. Certain sources claim that because most people are right handed the left nearside corner is the most likely position to attempt to ambush the unwary from. Once he has cleared his corner the point man turns to provide supporting fire to the other team members. For obvious reasons, the point man often has first choice on any body armour available. No 2 enters second and heads for the nearside right corner. No 3 (often the team leader) will head for the left far corner. No 4 will head for the right far corner. Often the fourth man does not enter the room and instead handles rear security.
Ideally 1 and 3 will take up a start position on the right side of a door, and the "evens" on the left. If a team is forced to retreat it does so in reverse numerical order.
In short, the drill is
Know your corner
Clear your designated corner.
Occupy the corner.
Fire on any other hostiles in the room.
A unit controls an area by field of fire rather than occupation. In other words there may be times when the team will shoot down any visible hostiles from outside the room before moving through the door. In such a case each man mainly concentrates his fire to the quadrant of the room he has been designated to move to. This means that 1 and 3 will fire into the left side of the room while being shielded by the wall to the right of the door, and visa versa for 2 and 4. There is an obvious advantage if the No.2 man is left handed and has a weapon he can fire from his left shoulder - so not the SA80. The wall will provide some cover and concealment but many modern bullets will penetrate such cover and it doesn't take a rocket scientist to work out were you are likely to be standing. If the enemy manages to respond with effective fire then it may be better to either retreat or advance into the room and take the fight to them. Corridors and many rooms will have several doorways and often there will not be enough personnel to clear them all at once. For this reason it is preferable to have a reserve that covers the clearing teams. If any other doors are opened then the support team is ready to fire upon them. Likewise, if a clearing team comes running out of a room the support unit will fire on anyone foolish enough to give chase.
Variations on a theme. Doorways are often located near the corner of a room, so there is no nearside corner or the space is insufficient for the No.1 or 2 man to occupy without hindering the movement of the other team members. In such a case the No 1 or 2 man follows the wall to the next corner. If the No 3 or 4 man sees his corner already occupied he should take up a position partway along the wall. The team therefore ends up in an L shape rather than a line Unless a room is very large, a clearing team will not be more than four men. In small rooms even this number may cause overcrowding and a three or two man team is used. In both such cases the above method is still used, but corners not occupied by team members are instead dominated by fire from the other corners. Trying to clear a room on your own is far from ideal, but again the same method is used. The first (and only) man takes the left nearside corner and controls the others with fire.
The above might be called the "Four Corners" method of room clearing. Simpler, and therefore preferable is the method shown at
The Point man going left is still a good idea, though this may be changed based on what is known of the room's layout or the situation that the Point sees as he enters. Another strategy is to head for the hinge side of the door if the door opens outward and for the handle side of the door if it swings in. Whatever way the Point man goes, the No.2 goes in the opposite direction, No.3 the same direction as the Point and No.4 follows No.2. No.1 and 2 head down the wall for the nearest corner, shooting down any hostile in their path and then turning to fire at any other targets. No.3 and 4 follow the path of 1 and 2 but stop before they reach the corner, usually a couple of metres past the entry point. They too turn and fire at any targets in the room. The team therefore form a line formation (or an L in a room with a corner door). Advantage of this method is that 3 and 4 do not cross the fire zone of 1 and 2 to reach the far corners and the same drill adapts to most room shapes.
Movie stuff. You may have seen cop shows where two detectives are about to kick down a door and one says "You go high, I'll go low". They kick down the door, each covers one side of the room, one dropping to a crouch. So what's wrong with that? Well, first, the comment should be redundant. Both of them should know the first man through will take the left of the room and that the one on the right of the door will go in first. Second, you don't stay in the doorway asking to be peppered with a shotgun. You either cover your sector of the room from behind the protection of the wall or you swiftly move through the door and into your corner of the room. Another thing you will see on the TV is a cop about to go through a door with his pistol up by his face. One writer, remembering 70's Cop shows talks of "The HIgh Starsky" and "Full Sabrina"! This makes a nice dramatic shot for the camera but is not too wise. If the cop encounters someone immediately on the other side of the door they could grab his arms and all he can do is shoot holes in the ceiling. A better way to go through the door is with the pistol pointed down, arms straight. If the arms are grabbed then you can still shoot at the perp's legs. Entering a room with your muzzle aimed down also allows you to use the quick reaction shooting techniques described on this page.