The US state of Virginia saw some 50% of the nation's Civil War casualties. Now, mass construction of AI data centres is encroaching on historic lands, the environment and local communities.

As the gunner of the Bull Run Legion lifts the explosive charge from its container and carries it up to the cannon, dozens of phones are lifted from pockets. Visitors open camera apps and raise devices high, focusing in on the handful of blue-uniformed men as they swab the gun's barrel with an era-appropriate sponge fastened to a stick.

The cannon blasts its shot out into the air, and in the same moment, each phone fires its parcel of data at the cloud, landing in a data centre where banks of diligent servers sort, clean and route it along.

On 21 July 1861, Union soldiers defending the United States watched over the crest of the same hills now framed on tourists' smartphones, as rebelling Confederate forces charged out of the forest in the first major battle of the American Civil War. A century and a half later, the Bull Run Legion, a group of "living historians" (better-known as re-enactors), still gather at Manassas National Battlefield Park using historic techniques and uniforms to commemorate that struggle.

But today, the march of technology has turned this historic landmark into the scene of a new kind of battle.

Technology companies are planning to erect one of the largest data centres in the world here at Manassas, Virginia, on the very ground where the Union army lost the war's first major land battle. Demand for data centres has skyrocketed as the artificial intelligence (AI) industry blossoms – but experts and advocates say the race for technological growth could threaten resources including water, energy and land. Some experts foresee a "growing crisis" for residents and future generations.

The concerns aren't just practical, however – some fear building data centres too close to national landmarks could erase history and bury the lessons the Civil War has for future generations. "Do I want to see a data centre on the view line of this park? No, I do not. But do I recognise, since I worked in IT, that they're necessary? Yeah, I can get that. So there is no easy answer," Bart Wheeler, one of the living historians who works the cannon, tells the BBC. "Any interested citizen has to be worried."

Those building the data centres disagree with these concerns and say they are taking steps to ensure the development is respectful of the historical context, even planning new information kiosks and trails around the site.

Now, around 150 years after the Union army fought to protect this land in the 19th Century, a coalition of community advocates, environmentalists and history buffs are waging a differenty kind of war against an industry they say is steamrolling past their interests. It's a conflict with global repercussions.

The infrastructure which makes the internet work often lives in massive windowless buildings ringed by high black fences. Inside, stacked banks of computer servers receive signals and crunch numbers from devices around the world, providing the technical horsepower that allows for viral videos, cheeky text messages and more recently, untold numbers of AI queries.

Data centres process our most intimate thoughts and transactions, but they're seldom seen by most users – that is, unless they're your neighbour. Around the world, the sprawling footprint of data centre development and their demands on resources have made this aspect of our digital lives more visible and controversial, particularly as the AI era sparks meteoric growth.

"Customer demand remains very strong, driven by the digitalisation of the economy and AI revolution," says Karen Cohen, a spokesperson for QTS Data Centers, one of two companies seeking to build the massive Prince William Digital Gateway data centre development at Manassas. According to the American Battlefield Trust, the 37-building complex is the largest planned data centre development on earth the world.

QTS and other data centre providers like it contract their servers out to other corporations, providing the backbone which makes the internet run. As the internet has grown, so has the industry's footprint in Northern Virginia: the region is already the

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