Hurricane Katrina stripped the roof off Navy Seabee Steven Sepulvado's house and flooded it, forcing his wife and two small children to flee even as he went to work aiding this decimated Gulf Coast town.

Then Rita roared in, ravaging what remained of Sepulvado's home.

"I was up all night fighting my tarps," said the 27-year-old Navy construction mechanic, who clung to his roof in the howling wind and rain, nailing pieces of scrap wood onto blue tarps after Rita popped them off. "I had to sit down a few times to keep myself from blowing off."

Now, with his life still in disarray and no home for his family, Sepulvado is preparing to deploy in about a month to Iraq's insurgent stronghold of Anbar Province, where his Seabee unit will be assigned construction jobs. Even so, he says, things could be worse -- until a delay came a few days ago he was scheduled to ship out for Iraq this week.

The story of Sepulvado and his 638-man Naval Construction Battalion is an extreme example -- but far from an isolated one -- of how the emergency deployment last month of more than 70,000 U.S. troops for disaster relief has exacerbated strains on a military already severely taxed by the wars in Iraq and Afghanistan.

Katrina and Rita sparked one of the biggest-ever mobilizations of American military forces -- National Guardsmen and active-duty soldiers -- for natural disasters.

The urgent response essentially maxed out the forces of the 82nd Airborne Division, which dispatched to the Gulf Coast nearly 4,000 paratroopers -- including a strategic brigade the Pentagon keeps on alert to jet to global hot spots on 18-hours notice. That left the 82nd, which has five infantry battalions committed to Iraq and Afghanistan, short of a full complement to form a new alert force. So the Army had to shift some missions to other units.

The 82nd also had to cancel, for October, one of two planned intensive, multimillion-dollar training exercises at the Army's urban warfare center at Fort Polk, La.

"It's put a strain on the organization, but we've done a good job of absorbing it," said Col. Tim McAteer, deputy operations chief for the 82nd Airborne Division at Fort Bragg, N.C. He said the paratroopers will resume regular missions and training once they return, as early as this week.

"It's an issue" balancing the competing demands on the forces, acknowledged Navy Adm. Timothy J. Keating, commander of U.S. Northern Command, which oversees active-duty forces deployed at home.

Tensions have arisen over the length of disaster duty for military forces -- especially the active-duty units -- with disputes among commanders over when troops, aircraft and ships can be released to catch up with demanding training and deployment timetables, military officials said.

Navy and Marine Corps officers aboard the USS Iwo Jima, an amphibious assault ship dispatched for both hurricanes, said last week the 1,100 sailors and 650 Marines aboard would have to accelerate certification and training to get ready for overseas tours to begin as soon as next spring. While rescue and security missions along the Gulf Coast allowed troops extensive practice in skills such as launching and flying helicopters off the ship, and urban foot patrols, it detracted from other combat training, the officers said.

In the broader debate over natural-disaster response, commanders and Pentagon officials have indicated that they do not support a new, expanded role for the active-duty military.

"I would favor, all things equal, the current system, where the guard is trained and equipped to provide first response capabilities with local and state authorities," Keating told reporters Thursday. Only in extreme cases, when first responders are overwhelmed, is there "a role to be considered for the active-duty forces," Keating said.

The hurricanes also placed new strains on the National Guard. At the height of the response, 50,000 guard troops were mobilized in the storm-struck Gulf Coast region, while 75,000 were deployed in 40 countries, including Iraq, where they make up almost half the U.S. force, according to official figures. Although they represented nearly a third of the total of 440,000 National Guard troops, many of the units called up in Mississippi and Louisiana, as well as those responding from Arkansas, Oklahoma, Washington and Ohio, came from occupations in heavy demand, such as infantry, military police and engineers, and had already served tours in Iraq or Afghanistan.

Two weeks after Katrina struck, the 2,500 troops from Louisiana's 256th Infantry Brigade returned from a year in Iraq and were immediately asked to volunteer for hurricane relief efforts; about 800 did. About 500 of the troops grappled with direct losses from Katrina.

In Gulfport, too, troops such as Sepulvado are struggling with the burden of being at once first responders, hurricane victims and war fighters.

"It's hard," Sepulvado said amid the bustle of pre-deployment medical checks at his battalion headquarters in Gulfport. Nearly 70 percent of the members of his battalion had their homes damaged, with the homes of 115 destroyed or unlivable.

Soon after Katrina plowed through, Sepulvado was sent to work at Gulfport's Hope Haven, a home for abandoned children. As he and comrades ripped out walls and carpeting, repaired shingles and moved appliances, they worried about their own catastrophes. "I was kind of thinking, 'What am I doing here?' " he said. "Why are we doing this when we lost our own homes?"

Like others in his unit, Sepulvado waits for an insurance check, hoping to get his family -- now living with parents -- settled before he deploys. His wife, like several other spouses, lost her job when her workplace was destroyed.

Although the Navy, Red Cross and agencies such as the Federal Emergency Management Agency have helped with $200 grants and other services, finances are tight.

Many of the Seabees, as the Naval engineers are called, were so busy laboring for others clearing roads and repairing schools that days passed before they had the shock of visiting their own homes.

"When I finally saw it, I was stunned," said Benjamine Carroll, 22. His solution was to work even harder hauling equipment from the base warehouse. "I was just trying to keep myself busy so I didn't think of what was going on, and then go to sleep."

Stephen Lucas, 25, drove his wife, 38 weeks pregnant, to safety in Knoxville, Tenn., then returned to hunt for his house in the Arbor Station complex popular among Seabees. "It was gone . . . it was a concrete foundation," said Lucas, whose daughter was born Sept. 12.

As they prepare to head to Iraq, many Seabees worry about how their families will get along. "It's nerve-racking," said Gary Pearson. He will soon move his wife and 7-month-old daughter to Texas because their Arbor Station home was damaged. But before they go, he plans to spend time looking at favorite photographs with his wife, singing songs to his daughter for the video camera, and reading the Bible "more than I used to," he said.

Gary Pearson, whose home was heavily damaged by Hurricane Katrina, hopes to relocate his family before his imminent departure for Iraq.