How riot control works:

Riot Control Tactics

The tactics used to control riots in the past were simple -- they were based on the fact that the police were almost always better-armed than the rioters. The tactics they used basically consisted of forming a line and charging into the crowd. Today, the police are still well-armed, but tactics have advanced significantly in hopes of preventing injuries.

When a riot is in full swing, police will deploy in a square formation with a command team at the center. The command team is protected on all four sides by echelons of troops deployed in groups of 10 or 12 officers. There is also an arrest team at the center of the square.

This tactical unit is very mobile and able to adapt on the fly to changes in the situation. If a threat suddenly appears behind or to one side of the unit, then the echelon facing that direction is designated the front of the unit. The entire team can then change the direction it's facing without a lot of maneuvering. Also, the echelons can cover each other when the team moves to take advanced positions. If the unit is under attack, the whole team does not move together: One echelon moves while the others provide covering fire or an actual physical screen (with riot shields). Then another echelon moves up into position.

The echelon is not meant to be an impenetrable wall of cop. In fact, the riot squad often leaves an escape route to let rioters run past the squad. The officers can adopt a passive position, in which they spread out and leave several yards between each officer. The crowd can then easily filter through them. If a particularly violent group moves toward the officers or they spot specific suspects they want to arrest, they can quickly close the gaps and form a tight line.

As the unit moves forward into a crowd, it will prod and push at anyone who doesn't respond to requests to move away by the time the front echelon reaches them. If they still refuse to move, the unit continues moving forward, but the front echelon opens up and passes around the protestors. Once the protestors are inside the square, the unit stops, the front echelon reforms and the arrest team processes the rioters. When they're done, the unit can continue moving.

Crowd-control Philosophy: Conflict

If a crowd gets unruly and starts taking violent action, then the police will switch to a more aggressive attitude. Their actions here reflect the fact that almost all riots are incited and lead by a few individuals who feel strongly or have something to gain from a violent confrontation. The majority of the people present either show up because something exciting is going on or are bystanders who got carried into the mob mentality. Faced with the possibility of arrest or confrontation with police, most of them simply want to escape and go home.

The first step is simple intimidation. Riot officers stand in strict formations and act with military precision. Once they form echelons -- lines of officers that effectively work as barriers -- the officers tap their batons on their shields or stomp their feet in unison. The result can be quite frightening to unarmed civilians -- it looks and sounds as if this group of armed and armored officers is getting ready to come crashing down with clubs swinging. In truth, this display is meant to scare off as many of the rioters as possible without the officers ever getting near them.

Police do not try to arrest every rioter. Their first targets are those who are leading the riot, because often the crowd will disperse without their leaders firing them up and encouraging them. All people who are spotted breaking a law are also targeted for arrest, especially if they injure or kill another person.

When it gets to the point where officers are actually in conflict with the rioters, the goal is still to disperse the crowd. A combination of advancing lines of officers and the use of noxious gas is used to direct the crowd in a certain direction or keep them away from a certain area. The crowd is never pinned down -- rioters are always given an escape route, since the whole point is to get them to run away.

Source: "How Riot Control Works" by Ed Grabianowski | howstuffworks.com