Tens of thousands of National Guardsmen called to duty in the Persian Gulf are being temporarily replaced in some states by volunteers whose duties include watching over vacant armories and assisting in natural disasters.

Usually called the state guard or the state defense force, groups totaling nearly 10,000 such volunteers -- mostly retired soldiers and sailors -- exist in 24 states and Puerto Rico.

"We're sort of a has-been force until we're needed," said Tom Anderson, president of the National Association of State Defense Forces.

Most have been relatively inactive in recent years, but Persian Gulf call-ups have expanded the role of these purely state-operated organizations, said Anderson, commander of the New Mexico State Defense Force.

"We have people from all walks of life. I would say that our membership is pretty much split between veterans as well as young people having no military service whatsoever," said Commander Robert Haas of the 750-member Ohio Military Reserve.

None of the organizations has federal status, although the Washington-based National Guard Bureau assists the states in coordinating their activities.

The governors can call up the state units to help with disasters and other activities usually handled by activated Guard units.

Size, duties and history of the units vary widely.

Texas has a 1,300-member state guard, and units in Tennessee and Georgia number about 1,000. Rhode Island's State Defense Force, created in 1987, numbers just three, and Vermont's eight-year-old state guard consists of 12 retired military officers.

The 400-member Indiana Guard Reserve last summer provided relief and assisted in the cleanup of southern Indiana, hit by devastating storms.

Last year, the Virginia Defense Force helped with crowd control at 17 events around the state. It has done search-and-rescue missions and is helping a small town develop a plan to handle toxic chemical spills.

Some of the units, such as Alaska's, were formed at statehood. Others were authorized by state constitutions and some formed during World War I. In Mississippi, the State Guard operated under an attorney general's opinion until the Legislature put it into law in 1989.

Many units have deep roots in U.S. history. New Mexico's militia traces its beginnings to an organization know as "Los Vecinos" (the neighbors), dating to 1606, when the Spanish explored the Rio Grande valley. Georgia's State Defense Force traces its heritage to a colonial militia organized in the Massachusetts Bay Colony in 1636.

In Michigan, the recruitment of military retirees begins in earnest next month. The Michigan Emergency Volunteers is re-emerging, after having flourished during the two world wars before being disbanded in 1946.

"We've had it before," said retired Brig. Gen. Warren Lawrence, who is to oversee the organization. "It's something that really should be in place, at least in skeletal fashion to activate on a needs basis."

Much of the state guards' work right now is voluntary. None has been called to duty by executive orders of governors. State units in a few states, if activated by the governor, would get the same pay as National Guardsmen.

"Right now, we're watching over about 55 National Guard armories across the state," said Maj. Gen. Roy H. Swayer Jr. of the Mississippi State Guard.

Members of the Tennessee Defense Force are repairing doors, helping with finances and otherwise aiding spouses of mobilized National Guard troops.

"We've gotten an enormous amount of volunteer work going on, with people assisting units that have mobilized -- lawyers helping draw up wills, helping with family support groups, things like that," said Brig. Gen. Frank Pointer.

Tom Hegele, a member of the North Carolina State Defense Militia, said the groups are true volunteers.

"This might not be much, but for some people it is a way they can contribute," Hegele said. "We're telling people who might have aged out of active service or the Guard to look us over and see if they're interested."