For more than a century, people who live near the Civil War battlefields of Chancellorsville and Fredericksburg have known that the wide, black arrows emblazoned across maps of their fields and rivers depict the spectacular surprise of Stonewall Jackson's flanking attack on the Union Army in May of 1863.

But new maps are making their way into the hands of those who live in history's back yard, and this time, the menacing black arrows chart the movements of another class of wily tactician, the real estate developers who lead the army of sprawl.

Ray Smith, commander of Dogwood Development Group in Reston, has set his sights on Mullins Farm, a 788-acre expanse of rolling hills and clusters of old trees where Union Gen. Joseph Hooker gave up the fight to Robert E. Lee's Confederate forces.

Smith is pushing hard for a rezoning that would allow him to build a new city of 1,995 houses plus more than a million square feet of retail and offices -- vanguard of a vast suburb stretching along a proposed outer connector highway, part of an eventual Fredericksburg beltway.

"The collision between preservation and development here is inevitable," says John Hennessy, acting superintendent of the Fredericksburg and Spotsylvania National Military Park, which includes Chancellorsville. "But juxtaposing a new urban center with a national park is just bad policy."

The roads here, sluggish Route 3 and bucolic Route 610, were Orange Turnpike and Ely's Ford Road during the Civil War -- "famous in battle reports in 1863, famous in traffic reports in 2002," Hennessy says. Huge trucks roar past earthworks as tourists strain to hear rangers' tales.

The kind of development that long ago hemmed in Arlington National Cemetery didn't hit Chancellorsville until recently, as Washington sprawl extends south. Spotsylvania's recovery took a solid century; the county didn't return to its wartime population until after Interstate 95 was completed in 1964.

Now, the county argues over two views of the future: Some people want to build on available farmland, believing that new housing and roads will lift all boats in a struggling county. Others say government pays far more to build the infrastructure needed to support such development than the new growth could generate in taxes.

The question is not whether to grow, but whether growth must happen 100 yards from the national park, says Hap Connors of the National Trust for Historic Preservation. "There's no need to put everything on Route 3," he says, suggesting Route 1 as a smarter development corridor. "You can have growth but also protect the economic resources that generate tourism."

The National Park Service saw this coming, but too late. In the 1920s, when the park was created, government policy was to buy only the physical remnants of war, such as battlements. The land where fighting occurred was left to the care of local farmers. That worked until places like Chancellorsville found themselves on the profitable edge of sprawl. Now, farmers are cashing in, and the Park Service scrambles to minimize the damage.

This administration is not eager to expand national parks. Still, preservationists want a shot at buying the land. If the county rejects Smith's plan before his options run out in April, existing zoning would allow the farm to be developed, but with only 235 houses. (The county planning commission takes up the issue tomorrow.)

The lesson of the Battle of Chancellorsville, still taught at military academies, is that a small, creative force can overwhelm a much larger army. Sadly, armies of preservation often do not gather until after a terrible loss; Loudoun County's slow-growth movement won power only after unchecked sprawl saddled the county with choking traffic and massive infrastructure costs. Must Spotsylvania live the pain before taking a stand?

A couple of miles toward Fredericksburg sits sad, living proof of how development can erase history: Old Salem Church, scene of fighting during the Chancellorsville battle, is preserved as a national park, but only barely.

The church grounds have been reduced to 1.5 acres, their native grace crushed by a cacophony of eight lanes of commuter madness, a vision of what Chancellorsville faces -- unless people say No.

E-mail: marcfisher@washpost.com