The Army is much better prepared today to respond to a major national disaster than it was in 2005 when Hurricane Katrina swamped New Orleans, but it’s still unclear how prepared the Army is for the disaster that planners fear most – a 10 kiloton nuclear explosion in a major U.S. city."We’ve come a long way in a few years," said Lt. Gen. Perry Wiggins, commander of the U.S. Army North, the Army command responsible for homeland defense. "But we still have a long way to go."Wiggins and a panel of military and civilian agency chiefs described the grim and chaotic aftermath of a nuclear attack.The blast would be devastating, they said during the Association of the United States Army’s Annual Meeting and Exposition. The Hiroshima blast was 16 kilotons.Buildings and other infrastructure would be destroyed or heavily damaged within three miles of the explosion.Thirty-thousand would be killed or injured, thousands more would suffer first, second and third degree burns. An electromagnetic pulse would destroy communications equipment.High levels of radioactivity would contaminate an area up to 12 miles from the bomb. And, perhaps, millions would be trying to evacuate the area, clogging streets and blocking the arrival of first responders.First on the scene would be local police, firefighters and emergency medical personnel. But their resources are limited and in a disaster this large, local and state agencies would quickly be overwhelmed.Police in Washington, D.C., for example, have protection equipment, dosimeters and the ability to decontaminate personnel who have been exposed to radiation, but just enough to last "for a day, maybe two," said Police Chief Cathy Lanier. They’re counting on the military or other federal help to arrive quickly."We know the feds are coming," Lanier said.The first "feds" on the scene might well be the National Guard, which has specially equipped and trained CERFPs – Chemical, Biological, Radiological/Nuclear, and Explosive (CBRNE) – Enhanced Response Force Packages – developed to respond to just such an attack."We can respond in hours, not days," said Lt. Gen. William Ingram, director of the Army National Guard.Since the Guard is a community-based force, it would likely have units based in the city.The guard’s CERFPs are tailored to search and extraction operations, for decontamination and to provide basic medical care to blast victims. They also have command and control equipment for coordinating with other responders.Beyond the CERFPs, the guard also has helicopters, trucks, and shelters that would undoubtedly be in demand, Ingram said.The Army Reserve would be another early responder, said Lt. Gen. Jeffrey Talley, Army Reserve chief.The Army Reserve has 2,300 soldiers specially trained to respond to chemical, biological, radiological, nuclear and high-explosive incidents, he said. It also possesses much of the Army’s combat support capability, so it could provide medical transportation, aviation, water, fuel, engineers and other support capabilities.Like the National Guard, the Army Reserve is a locally-based force with a presence in 1,100 communities nationwide, Talley said. In response to a major disaster, Talley said he would immediately order Army Reserve troops to active duty."I’m the commanding general of the Army Reserve and I don’t need anyone’s permission to do that," he said.The response to a nuclear explosion would quickly become "a whole of government response," with the Federal Emergency Management Agency in the lead and dozens of agencies, from Customs and Border Protection to the Coast Guard lending support.Customs and Border Protection, for instance, operates "the largest civilian air force in the world," said Michael Fischer, chief of the U.S. Border Patrol. It could provide light observation helicopters, heavy lift helicopters and Predator unmanned surveillance aircraft, he said.Private companies and non-governmental organizations would also be tapped, Wiggins said. And in all but the most extraordinary circumstances, the military would remain in a supporting role, he said.The Army isn’t used to that. When they deploy overseas, Army commanders are used to being "large and in charge," but in the homeland local police, mayors and governors are in control."One of the scariest moments" during the response to Hurricane Katrina, Wiggins recalled, came when a local deputy sheriff who was having trouble with gangs wanted to deputize members of a Green Beret platoon.The lieutenant platoon leader "thought that was a good idea" and was ready to go along until more senior officers halted the plan."Career genocide in the homeland can happen in a nanosecond," Wiggins said. "You have to know the laws."Key among the laws is the Constitution, which imposes broad limits on the power of the federal government, said Bernd McConnell, former head of the Dual Command Interagency Coordination Directorate for the North American Aerospace Defense Command and the U.S. Northern Command.It’s sometimes hard for military personnel accustomed to hierarchy to grasp that "mayors don’t work for governors, and governors don’t work for the president," he said.Even though the military isn’t in charge during domestic disasters, "the American people have high expectations [of the military] here in the homeland," Wiggins said.Adding, "And we only have one chance to get it right."