Order amid chaos: The Marines train for combat (pictures)

As the morning begins, instructors at the Infantry Immersion Trainer lay out the gear that Marines will use as they train. The troops will be firing live but will use special bullets topped with soap that are essentially like paintballs. Here, one of the instructors lays out the muzzles that are used to shoot the special bullets.

Members of the Marines' 6th Engineer Support Battalion -- a reserve unit -- have come to Camp Pendleton from their bases in Tucson, Ariz., and Bakersfield, Calif., to take part in the Infantry Immersion Trainer.

Although they will be firing special, non-lethal ammunition, they must still wear protective gear, such as the masks on the left. On the right are magazines full of the special ammunition.

Marines line up to get their gear for their day at the Infantry Immersion Trainer. They are carrying M-16s without muzzles and will be given a muzzle that has been configured for shooting the special, non-lethal ammunition.

A Marine inspects his M-16 as he and his fellow troops mill about prior to beginning their day at the Infantry Immersion Trainer.

Major Lucas Castanos of the U.S. Marines 6th Engineer Support Battalion briefs his troops on what they'll be going through in the Infantry Immersion Trainer.

A squad of Marines puts on their protective masks as they prepare to enter the Infantry Immersion Trainer.

An instructor named Darren briefs a group of squad leaders on the layout of an indoor "town" they'll be leading their troops into. Each squad would enter the town on "presence patrol" and would have to suppress an insurgent that fires at them.

Several Marines point their weapons down an alley as they patrol the "village" that is meant to resemble an Afghan town.

A Marine kicks open a door during his squad's patrol.

The sniper has opened fire on the Marines as they've entered a public marketplace. Here, a Marine runs across the square firing at the sniper's position as several of his squad cover him.

Before the Marines arrive, several "villagers," civilians hired by the Marines to help make the IIT more realistic, mill around the marketplace.

A Marine runs out from behind a wall shooting.

Darren, the IIT instructor, kneels as he looks on at the Marines going through the scenario inside the Infantry Immersion Trainer.

This is one of the non-lethal bullets used in the IIT training. It is topped with a material made from soap that leaves marks, but won't injure or kill those it hits.

A squad of Marines prepares their weapons for the trainer. They are facing the fence because it guarantees they won't accidentally fire their weapons at anyone.

Marine Sgt. Gerry Apple goes over the plan for his squad as they ready to enter an outdoor "town" that is part of the Infantry Immersion Trainer. Marine Capt. Jeremy Masten (foreground) looks on and offers feedback.

A squad of Marines enters the outdoor area of the IIT, which is meant to resemble an Afghan town.

A Marine shakes hands with a "villager." The Marines are trained to try to maintain cordial relationships with the locals.

Two Marines peek around a narrow corner as they patrol the outdoor area of the trainer, trying to find a shooter who has opened fire on their squad.

An instructor watches several Marines as they are about to make their way through a bottleneck. The instructor is shouting various commands and feedback at them as they work.

The squads are accompanied by a "translator" who helps them converse with the locals. Here, the translator fires at an attacker as the squad has gotten caught in a surprise attack.

The Infantry Immersion Trainer is designed to prepare the Marines not just for dealing with with attackers firing at them with guns. In addition, it features other surprise dangers, including improvised explosive devices.

Instructors also serve as referees, calling out when someone is shot or "killed" by something like an IED. Here, several Marines run over to help a comrade who has been "hit" by an exploding IED.

Three Marines cover another who is carrying a "wounded" comrade over his shoulder.

A Marine runs in the middle of a scenario in the Infantry Immersion Trainer.

A Marine drags off a wounded comrade in the middle of a training scenario.