Under crystalline winter skies, a light infantry unit headed for Iraq was practicing precision long-range shooting through a pall of smoke. But the fire generating the haze had nothing to do with the training exercise.

Staff members at the Army post had set the blaze on behalf of the red-cockaded woodpecker, an imperiled eight-inch-long bird that requires frequent conflagrations to preserve its pine habitat.

Even as it conducts round-the-clock exercises to support two wars, Fort Stewart spends as much as $3 million a year on wildlife management, diligently grooming its 279,000 acres to accommodate five endangered species that live here. Last year, the wildlife staff even built about 100 artificial cavities and installed them 25 feet high in large pines so the woodpeckers did not have to toil for six months carving the nests themselves.

The military has not always been so enthusiastic about saving endangered plants and animals, arguing that doing so would hinder its battle preparedness.

But post commanders have gradually realized that working to help species rebound is in their best interest, if only because the more the endangered plants and animals thrive, the fewer restrictions are put on training exercises to avoid destroying habitat.

In the early years of the administration of President George W. Bush, the military lobbied Congress for limited exemptions from federal protection rules.

Today, herculean efforts to save threatened species are unfolding at dozens of military sites across the nation, from Eglin, Fla., where the Air Force has restored and reconnected streams for the Okaloosa darter, to San Clemente Island, Calif., where the Navy has helped bring the loggerhead shrike back from the brink of extinction.

“Ten years ago, you would have had three- or four-star generals stomping up and down” if the Pentagon ordered such measures, said Tad Davis, the Army’s deputy assistant secretary for environment, safety and occupational health. “Now they just ask, ‘How do I get it done?’ ”

As the owner of some 30 million relatively pristine acres that are often critical habitat for plants and animals, the military is laboring to fulfill its remaining obligations under federal laws like the Endangered Species Act without curbing its training exercises.

But its work also reflects a new dedication to protecting the natural environment, said L. Peter Boice, the Pentagon’s deputy director of natural resources.

“There is a strong understanding now that land is a limited resource, and that even our military is part of a larger ecosystem,” he said. “If that degrades, it is harder for us to do our mission.”

From 2004 to 2008, the most recent year for which data is available, the Department of Defense spent $300 million to protect endangered species — more than it spent in the previous 10 years combined, Pentagon figures show.

Now the military plans to broaden those efforts, reaching beyond the 420 officially endangered or threatened species on its land and restoring ecosystems for more than 500 others that are considered at risk. Training post commanders on environmental responsibilities is now routine as well.

The military began scooping up wide-open and largely untouched rural expanses in the late 1930s and early 1940s as the country prepared for World War II. But decade by decade, suburban sprawl has brought development literally up to the back fences of installations, turning them into de facto havens for many threatened animals and plants.

Preserving those species can require frustrating adjustments. At certain times each year, for example, the Marines are able to use only a fraction of the beachfront at Camp Pendleton, Calif., to practice amphibious landings out of concern for nesting shorebirds like the coastal California gnatcatcher.

In some cases, colliding priorities have not been reconciled. The Navy still relies heavily on midfrequency sonar, for example, riling environmentalists who say it disrupts activity by whales and dolphins off the California coast.

Still, for every clash there is an instance of intense efforts to keep an animal safe. At Twenty-Nine Palms, Calif., for example, the Marines built a desert tortoise research and rearing center in 2005 to help the soft-shelled babies avoid predation by ravens.

Such efforts have won over some of the Pentagon’s toughest environmental critics. “Over all, the military has done a great job, and I know they are spending boatloads of money,” said Kieran Suckling, executive director of the Center for Biological Diversity. “When they decide we are going to protect something, they just do it.”

Of course, it took years for the Army to hit on a workable strategy for the woodpecker — a lesson that is informing its conservation work today. The bird first caused a minicrisis at Southern installations like Fort Bragg and Fort Stewart in 1990, when troops were preparing for the war to oust Iraqi troops from Kuwait.

To protect the woodpeckers, tanks were prohibited from going into some parts of the forest where the birds had nests. But that strategy helped no one: the bird population did not increase, and the tanks had less room for their maneuvers.

Tim Beaty, the wildlife staff supervisor, held an eastern indigo snake; a young pine tree stood amid the ashes after a controlled burn that helps preserve the habitat of the red-cockaded woodpecker; and one of the birds looked for food.

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Slowly, the military realized (and was able to convince others) that it was not enough to protect the trees the birds were in; it had to create as much hospitable habitat as possible.

“As the Army realized what that habitat looked like, open and sunny, they realized that was good for soldier training as well,” said Tim Beaty, a civilian who supervises the wildlife staff at Fort Stewart.

Fort Stewart has long used controlled burning in its busiest training areas to prevent live ammunition from causing unplanned fires. Local species gravitated toward those scorched open areas.

So the post began systematically burning its entire land area, 500 acres to 1,000 acres at a time. After each burn, it planted longleaf pines and native wire grass, flora that dominated the area before European settlers arrived centuries ago. The woodpecker population rebounded.

Tanks are now allowed to drive right up next to some of the woodpecker colonies. Cameras placed in their nests by Mr. Beaty’s team had shown that the birds were indifferent to live-fire exercises.

Yet the success gave the Pentagon a new concern: without additional pristine habitat for species near its installations, “uncomfortable tradeoffs” could jeopardize training in years to come, said Janice W. Larkin, outreach coordinator for the Defense Department’s Sustainable Ranges Initiative.

So to limit pressures from encroaching development, the military began getting Congress to pay for preservation purchases in the 2005 fiscal year. By the 2009 fiscal year, the budget had grown to $56 million.

The Pentagon does not want to own those lands but organize multiparty partnerships. Fort Stewart, for example, has formed a partnership with the Georgia Land Trust, the Georgia Department of Natural Resources and the county government to try to preserve 100,000 acres on the edge of the post. Right next door, the Marine Corps’ Townsend Range is working with the Nature Conservancy to protect another 15,000 acres of critical watershed on the Altamaha River.

Although the installations’ goal is to prevent development from inching too close, the land will be a haven for threatened species ranging from a rare kind of mint to the gopher tortoise, which lives in sandy underground burrows. The Army wants to prevent the tortoise from being officially listed as endangered, which it says could seriously impede training on the post.

Alison McGee, a biologist with the Nature Conservancy in Georgia, said the Pentagon’s commitment allowed local groups to be more ambitious in rebuilding the natural ecosystem.

“It’s the military,” she said. “They make it possible to work at a really large scale.”