Look to your right: The coworker sitting next to you at this moment could soon be among the more than 15,000 "citizen soldiers" already called to fight in President Bush's war on terrorism.

These Reserve and National Guard troops, or "weekend warriors" as they are often called, have prepared for their missions by attending a minimum of one weekend's training every month, and two full weeks annually.

These soldiers are obliged to leave their workaday jobs behind when duty calls. And duty is certainly calling now.

After the terrorist attacks of Sept. 11, Bush authorized a partial mobilization of up to 50,000 Reserve and Guard troops, the largest of its kind since the 1990 troop buildup for the Persian Gulf War.

The numbers are sure to increase with Bush's call Thursday for protection at U.S. commercial airports. The president has urged governors to call up National Guard units to protect airports in their states while he implements a long-term plan to secure airlines from terrorist attack.

The package includes putting the federal government in charge of airport security, using more federal marshals aboard commercial airliners, modifying airplanes to restrict access to cockpits and so on.

"Fully implementing the extensive security proposal may take four to six months," a White House statement said. "During that time, the president will help ensure that every airport has a strong security presence by asking the governors of the 50 states to call up the National Guard — at the federal government's expense — to augment existing security staff at every commercial airport nationwide."

But the primary job of these soldiers is to defend U.S. soil, Pentagon officials say. Some — officials won't say how many — will go overseas, where Bush has promised to retaliate against Usama bin Laden and his supporters, prime suspects in the terror attacks.

Secretaries of the Army, Navy and Air Force have laid out a need for some 35,000 reservists, and troops are being called up as the services figure out where and with what kinds of duties they need help.

Those called for duty in the states are now doing jobs from intelligence collection to public relations to traffic control.

Another big need is to bolster the safety of military men and women on bases across America, and that is under way with the call-ups that began Sept. 20.

Duties might include patrolling base perimeters, checking cars and cargo that come and go and performing a host of other military police duties.

Forty-seven Air Force Reserve military police officers assigned to Travis Air Force Base's 349th Security Forces Squadron began work Wednesday at the base near Fairfield, Calif. Several dozen security troops at Charleston Air Force Base in South Carolina have been called up for guard and other duties at that base.

The Pentagon called up 635 additional military reservists on Wednesday. Those tapped included Seabees and other naval reservists and security forces with an Air Force special operations unit in Florida. Their call-up brought to about 15,600 the number called to active duty since Sept. 20.

Others had swung into action before that.

Almost immediately after the attacks on New York and Washington, guardsmen worked side-by-side with New York police and firefighters to clear rubble in the search for victims at the World Trade Center. Air Force reservists from the Puget Sound area were flown to the nation's capital to help identify victims of the attack on the Pentagon.

Normally, only 20 fighter-interceptors are on 24-hour alert to protect against violations of U.S. and Canadian airspace. After the attacks, Defense Secretary Donald H. Rumsfeld ordered jet fighter-interceptors at 26 bases to be ready to launch with 15 minutes notice and combat air patrols over Washington and New York to guard against both plane and missile attack. A number of Reserve units have been called to help with those efforts.

Ports and other waterways are being guarded in New York City and Boston by Coast Guard reservists from Florida.

New York National Guardsmen are controlling traffic, patrolling and escorting evacuated residents.

Members of an Army Reserve mortuary unit from Puerto Rico will help recover remains of the more than 6,000 missing from the attack on the World Trade Center.

But many of these heroes do not seem to mind the work.

"When you are sitting in your living room, and you're watching all the devastation happen in New York and Washington, you want to do something to help," said Brenda Barker of Little Rock, Ark.

A captain in her state's Air National Guard, she volunteered to leave her family and a fledgling desktop publishing business to do at least 45 days as a public affairs officer at Tyndall Air Force Base in Florida.

Others have said they've been told to prepare for active duty hitches of up to a year or, for call-ups with certain specialties, up to two years.

The Associated Press contributed to this report.