The Defense Department is stepping up its efforts to defend the Pentagon against terrorist threats, creating a police agency that can handle chemical, biological and radioactive attacks and teaching everyone in the building how to react in such situations.

In response to an internal review completed after the Pentagon was hit by a hijacked plane on Sept. 11, Deputy Defense Secretary Paul D. Wolfowitz this week signed an order creating the Pentagon Force Protection Agency, a defense official said yesterday, speaking on condition of anonymity.

The agency will absorb all functions now performed by the the Pentagon's police force, the Defense Protective Service, and will have expanded security responsibilities, officials said.

In another step, the Pentagon will begin using CD-ROMs this month to train the more than 20,000 employees in the building how to respond to such attacks.

In addition, a new public address system will soon be installed along the 17 miles of Pentagon corridors, replacing antiquated, frequently unintelligible squawk boxes. Computer networks are also being upgraded so that warnings will pop up on workers' computer screens.

Yesterday, area fire and police agencies staged a major exercise at the Pentagon to train rescue workers how to respond to a chemical attack.

A plume of smoke erupted from a concrete planter in the building's center courtyard yesterday morning, and soldiers in combat fatigues dropped to the ground, "victims" of a sarin nerve gas attack.

As the thick white smoke wafted through the courtyard, some of the role-playing service members in Operation Misty Court were laughing, hamming it up with extra histrionics for the long bank of cameras recording the event. Air Force Tech. Sgt. Cheryl White was not one of them. White had been at the Pentagon on Sept. 11, and for her, yesterday's exercise hit close to home.

"It was weird to be in there seeing the smoke," said White, 35, a Stafford County resident participating in the exercise. "I actually flashed back to September 11."

The scenes that followed accentuated the feeling, as Arlington County firetrucks converged on the Pentagon and rescue personnel wearing gas masks and chemical protective gear guided White and other designated victims past more seriously injured "casualties" lying in the grass.

"To see the 'dead and wounded,' it threw you," White said. "You felt that anxiety again."

Anxiety is the driving force behind a variety of efforts to improve defenses at the Pentagon.

"The existing structure is not an optimal solution for opposing subsequent acts of terrorism and other emergencies," Wolfowitz wrote in a letter to congressional leaders. "What is needed is a single [organization] that can provide a focused, streamlined and multi-disciplined force."

The new agency will have an expanded charter enabling it to take on more law enforcement roles -- including anti-terrorism efforts -- than the present force, which is largely focused on building security, a defense official said. The agency will have a larger budget than the police force and will probably be expanded from about 250 uniformed officers to about 300.

Some of the steps, such as training and improved communications, were being considered before September's attack, but "after the 11th, everything was accelerated," said Pentagon police chief John Jester, who will be the new agency's acting director.

Likewise, the Arlington County Fire Department had planned long before Sept. 11 to hold a chemical attack exercise, but after the terrorist attack, local and federal officials agreed that holding the event at the Pentagon would be appropriate.

The exercise, funded by the Department of Justice's Domestic Preparedness Program, involved more than 300 participants and included fire departments from Fort Myer, Alexandria and Arlington and Fairfax counties, as well as the FBI, Virginia State Police and area hospitals.

The scenario yesterday involved about 100 military service members gathered in the courtyard for a ceremony, a common sight at the Pentagon in warmer months. As they milled about, a simulated explosion released what was supposed to be sarin gas, the deadly agent used in the 1995 attack on the Tokyo subway system.

Screaming victims lay around the courtyard, each with an orange placard around the neck to identify symptoms. Makeup added to the effect, with some victims seemingly bloodied by wounds and others with blue faces, a sign of sarin poisoning.

Within minutes, members of the Pentagon police force responded in white chemical protective gear, carrying newly acquired chemical detection devices.

Arlington firefighters, alerted by the Pentagon police to the purported chemical attack, donned protective gear and drove into the courtyard through a corridor on a low-riding firetruck. Inside, firefighters doused victims with water to decontaminate them. Others used knives to strip fatigues off "unconscious" victims.

For White, walking around in a white gown after being stripped of her fatigues, the experience had been a little unnerving. "It was almost like reliving September 11," she said. "But you understand the reason for doing this."

Navy Lt. Jill Quinton, top, waits outside the Pentagon for treatment during the drill. Her symptoms included "extensive swelling on forehead and bleeding from the nose." Above, a victim of the sarin gas attack is doused with a fire hose to decontaminate him. Curious workers watched the drill unfold from windows and staircases overlooking the courtyard. Victims of the mock attack wore orange placards around their necks that described their symptoms. Makeup added to the effect. Smoke fills the Pentagon courtyard as the "victims" of a simulated sarin gas attack await medical treatment. "It was weird to be in there seeing the smoke," said one woman who took part in the drill. "I actually flashed back to September 11."A medic dressed in protective gear tends to a Pentagon worker during the drill. The exercise involved more than 300 people and four area fire departments.