COLORADO SPRINGS, COLO. ? The U.S. military has devised its first-ever war plans for guarding against and responding to terrorist attacks in the United States, envisioning 15 potential crisis scenarios and anticipating several simultaneous strikes around the country, according to officers who drafted the plans.

The classified plans, developed here at Northern Command headquarters, outline a variety of possible roles for quick-reaction forces estimated at as many as 3,000 ground troops per attack, a number that could easily grow depending on the extent of the damage and the abilities of civilian response teams.

The possible scenarios range from “low end,” relatively modest crowd-control missions to “high-end,” full-scale disaster management after catastrophic attacks, several officers said.

Some of the worst-case scenarios involve three attacks at the same time, in keeping with a Pentagon directive earlier this year ordering Northcom, as the command is called, to plan for multiple simultaneous attacks.

The war plans represent a historic shift for the Pentagon, which has been reluctant to become involved in domestic operations and is legally constrained from engaging in law enforcement. Indeed, defense officials continue to stress that they intend for the troops to play largely a supporting role in homeland emergencies.

But the new plans provide for what several senior officers acknowledged is the likelihood that the military will have to take charge in some situations, especially when dealing with mass-casualty attacks that could overwhelm civilian resources.

“In my estimation, (in the event of) a biological, a chemical or nuclear attack in any of the 50 states, the Department of Defense is best positioned – of the various eight federal agencies that would be involved – to take the lead,” said Adm. Timothy J. Keating, the head of Northcom, which coordinates military involvement in homeland security operations.

The plans present the Pentagon with a clearer idea of the kinds and numbers of troops and the training that might be required to build a more credible homeland defense force. They come at a time when senior Pentagon officials are engaged in an internal, year-long review of force levels and weapons systems, attempting to balance the heightened requirements of homeland defense against the heavy demands of overseas deployments in Iraq, Afghanistan and elsewhere.