Even for a force formed before the foundation of the Republic, what lies ahead for the National Guard along the Gulf Coast is something unprecedented in terms of scope.
"We're making history again," says Lt. Col. Robert Horton of the Alabama Guard. "Never before have we supported so many state and federal missions."
If the Iraq war showcases how Defense Secretary Donald Rumsfeld has recast the National Guard - turning it from a reserve deployed only in times of crisis to an active, operational force - then the aftermath of hurricane Katrina will go a long way toward determining whether this new mission is spreading America's part-time soldiers too thin, further taxing an already stressed force and endangering the nation.
Though Iraq has strained the National Guard, Defense officials have insisted that there are enough soldiers at home to deal with any domestic disaster. Now, with some Guard members comparing New Orleans to Baghdad after the fall of Saddam Hussein - gripped by chaos and looting - the Pentagon will have to prove its calculations correct.
"This is the test case for the National Guard," says Daniel Goure, an analyst at the Lexington Institute in Arlington, Va.
In all, some 21,000 National Guard troops are either on duty along the Gulf Coast or will be deployed there by the weekend - with 18,000 of those in Louisiana and Mississippi alone. To these, the Pentagon has added 7,000 active-duty soldiers, mostly from the Navy, making the response to Katrina the largest relief effort ever for the United States military.
It comes at a time when 138,000 troops - including 80,000 members of the National Guard - are deployed in Iraq. So far, the dual deployment has not hurt rescue efforts, National Guard officials say. Though more than one-third of the Mississippi and Louisiana National Guard forces are in Iraq or Afghanistan, other states can help plug any gaps.
But outbreaks of violence in New Orleans hinted at the potential for wider unrest and further call-ups, which could reveal weaknesses elsewhere in the nation. "What do we do if there is a terrorist attack?" asks Lawrence Korb, a defense analyst at the Center for American Progress here. "We're increasing our risk."
Yet in Florida, at least, National Guard officials are confident that they have enough soldiers to help out in Mississippi and also remain prepared for any other disaster. Even with troops in Iraq and Afghanistan, as well as Mississippi, the state will have more soldiers on hand than it needed last year, when four hurricanes hit Florida's coasts.
The concern, however, is that the repeated deployments are turning weekend warriors into full-time soldiers - and perhaps dampening their enthusiasm to continue serving. Although the National Guard's mission in Iraq and Afghanistan has clearly hurt recruiting nationwide, retention has remained strong. Another deployment to the Gulf Coast, however, could stretch the limits of how much part-time soldiers are willing to take.
"It's the families we're concerned about, because here we go again, we have to answer the call to duty," says Horton of the Alabama National Guard.
He estimates that some 90 percent of the Guard has been called to combat since Sept. 11. In Florida, Lt. Cmdr. Luis Sierra returned from Iraq last year only to find that six months later he was needed for three months of hurricane duty. Now, he's getting ready to ship out to Mississippi.
He's happy to do it. "Helping people out is the main concern," he says.
But his tone turns when he thinks about New Orleans. He says he would do it, but "To go over there would be like being in Baghdad again. There was looting, there there was no gas ... and a lot of desperation - it was a mess."
President Bush has cautioned that the rebuilding process will take months - even years - and Lt. Col. Ron Tittle of the Florida National Guard says commanders are "asking volunteers to be prepared for [a deployment lasting] months."
The heightened role of the active military in disaster relief could help ease the burden. While the active military has always been involved in disaster relief on some scale, the creation of a command center specifically designed to deal with disasters and homeland security after 9/11 has resulted in a military response that is "more robust, quicker, and more accurately targeted," says Lt. Cmdr. Sean Kelly of NORTHCOM.
This response is not a stopgap for an overextended National Guard, the Pentagon and others suggest. Since Sept. 11 "the system has become more flexible," says Dr. Goure. "We're seeing how the system was designed to work, regardless of Iraq."
Yet protracted relief efforts could present a problem. The Pentagon's plans had "always been for short wars and short disaster relief," says Goure. The solution, he says, will be help from other states. There are an estimated 125,000 Guard soldiers in the states along Katrina's storm path.
"They all receive the same type of training and can help backfill" for soldiers serving overseas, says Mike Stone, spokesman for the Florida Division of Emergency Management. "The silver lining is that we've had so many of these events in the past year that we're very well rehearsed."