If U.S. Northern Command needs troops to respond to a national emergency, commanders now have 4,000 Soldiers on alert to answer the call.

Northern Command at Peterson Air Force Base, Colo., which was created after the Sept. 11 attacks to coordinate the military response to everything from the aftermath of hurricanes to nuclear fallout, has relied primarily on part-time National Guard troops.

That changed last week with the Army announcing full combat brigade will be on alert for the next year, ready to roll out nationwide.

Despite conspiracy theories that this could be a first step toward martial law in the U.S., there won't be tanks on Main Street or active-duty troops putting down demonstrations. That is barred by federal law banning the military from being used on U.S. soil for domestic law enforcement.

Instead, the Soldiers of the 1st Brigade, 3rd Infantry Division at Fort Stewart, Ga., have been training to back up civilian authorities in providing medical care and dealing with chemical, biologic, high explosive or nuclear attack.

"My hope is you never have to use them," said Maj. Gen. Daniel E. Long of Fort Monroe, Va., who commands Northern Command's task force for civil support.

They'll be assigned to Northern Command for the next year as a fire brigade and will be replaced by another Army brigade in 2009.

"We haven't had a force for more than a two-week period that has been dedicated," said Lt. Col. Rob Cunniff, who works in the future operations planning division of the command's Colorado Springs headquarters.

Even without its own brigade, Northern Command hasn't been on the sidelines in disasters. From wildfires in California to the devastation of Hurricane Katrina, commanders at Peterson have delivered military help.

But with the new unit, commanders know they have forces that are properly trained for the challenges of disaster relief.

"They are clearly better prepared," Cunniff said.

The brigade's commander, Col. Roger Cloutier, said his Soldiers, recently returned from Ramadi, Iraq, are excited about being assigned to help in America.

"As I talked to people they realize what a huge commitment the government is making to keep Americans safe and free," Cloutier said.

Cloutier said his Soldiers are learning how to clear roads blocked by debris and how to uses the Jaws of Life to free trapped victims.

Other tasks the Soldiers have practiced include getting relief supplies to victims and setting up medical care facilities.

The new mission also means using different gear. Cloutier said the brigade's heavily armored tanks and Bradley fighting vehicles won't be useful in a disaster. When Northern Command calls, the brigade's troops will roll out in trucks and Humvees that are better suited to non-combat tasks.

Cloutier said he's also drilling his troops on the rules they face when operating on American soil. His Soldiers won't act as cops, and other wartime Army tasks like intelligence gathering also are forbidden in America.

And while the Army is used to being in the lead, on domestic missions, they'll be followers.

"We're in a support role to a lead federal agency," Cloutier said. "Every mission we do would be at the request of local and state officials."

Long said he's happy the Army will be there when the nation needs them most.

"It's a noble mission," he said.