The United States military is preparing for the worst.

  That may sound confusing because some say they are already knee-deep in the worst in places like Afghanistan and Iraq.

  But this worst is what could happen on American soil.

  KSPR's Joanna Small reports from Camp Atterbury in Indiana, where Missouri soldiers are training for a brand new mission that has the potential to change the way our military is perceived.

  It's dawn, but the sun's position has no signifiane at the Jennings County, Indiana, fairgrounds.

  Most there never went to sleep.

  "We got up about 4 o'clock in the morning, convoyed out, and we've been clearing the area for probably about seven or eight hours now," says Staff Sergeant Timothy Yardly, who is clearing rubble from a block roadway.

  He is working at Ground Zero.

  15 miles south the fairgrounds are home base for the 4th Maneuver Enhancement Brigade out of Fort Leonard Wood, the men and women tasked with repairing the mess nearby.

  "We chose to do the nuclear detonation. It's the largest most catastrophic of all the planning scenarios," explains Captain Bob McCullough.

  500 soliders from Fort Wood, along with 4,000 others from around the country are participating in a military first- a test-run for the CCMRF mission.

  They have turned Camp Atterbury's Urban Training Center into a mini-Inidianapolis, the epi-enter of a deadly nulear explosion.

  "What we're doing is trying to wet down our marine to get the contamination to stick to to the suit so it's not flying all over," a marine decontaminating one of his fellow comrads tells us.

  The military isn't fighting, they aren't armed; they are here working for state and loal agenies as first-responders.

 "They're working against an old paradigm.  Instead of coming in and taking over the incident, they're in support of it," explains the incident commander- and civilian- Tom Phillips.

  He's not affiliated with the military, yet he controls the situation.

  The troops are back-up, invited in- if this were real- by state offiials and arriving two days after the disaster, when all other resoures are exhausted.

  The only exception is the marines.

  Their job is to get to the disaster area as quickly as possible.

  That's because they're tasked with search and rescue. 

   Others decontaminate, others and each other, or evacuate.

  "We've been waiting on the army to show up here and evacuate these prisoners," a solider acting as a police officer in charge of a  jail explains.

  Some are clearing roads, while more still are repairing the stuff that repairs the stuff.

 "We are the central maintenance for the whole task force. If it breaks they bring it to us, we fix it, and give it right back to them," says Sergeant First Class John Baze.

  The goal is to have this "city" in working order in thirty days.

  An aerial view of the remnants of the explosion reveals that is quite a task.

  Now a force 4,500 strong will know how to takle it.