For hour after hour Thursday night, television viewers witnessed something never seen before: live pictures of American ground forces in the act of invading a foreign country, in this case racing unopposed across the battlefield of southern Iraq.

The images were often herky-jerky, sometimes blurry, and quite literally gritty, given the shifting desert sands. But the fact that they existed at all represented a milestone in the long and vast efforts to document warfare.

The war, live from the front lines and on the move, was made possible by what pundits instantly dubbed "tankcam."

The extraordinary shots were the product of newly improved videophones and mobile satellite uplinks. The rigs have been hitched to network-owned Humvees and retrofitted satellite trucks that are running, "Mad Max"-style, alongside the columns of American armored vehicles.

It wasn't so much what the tankcams showed, as the fact that they could show anything at all from 7,000 miles away in the middle of a barren war zone. Imagine witnessing the Charge of the Light Brigade from the safety of your living room.

On CNN, for example, correspondent Walt Rodgers bounced along as a churning spearhead of Marines zipped past a Bedouin goat herd. NBC's David Bloom showed viewers the endless, trackless, dun-colored moonscape. Crossing the border from Kuwait, Fox News's Greg Kelly was with the troops as they rolled past a sign in Arabic reading "Welcome to Iraq."

"It's very powerful and a little eerie," said Kathryn Kross, CNN's Washington bureau chief. "Just when video games are starting to look more like real action, the real action looks like a video game. Marshall McLuhan must be spinning in his grave."

The imagery on NBC, CNN, Fox News Channel and CBS was so dynamic that it made Ted Koppel's live, but static, field reports on ABC seem almost stodgy by comparison. Koppel, embedded with American troops on the Kuwait-Iraq border, had videophone and satellite-uplink equipment, but lacked the mobile antenna that makes a continuous picture aboard a moving vehicle possible.

CBS's battlefield Humvee has five cameras, carries its own fuel and a generator that runs off its engine. The vehicle's windows and camera lenses have been outfitted with polarizing film to prevent glare. It's air-conditioned and comes with "run-flat" tires that don't require air.

NBC's pictures were by far the cleanest, thanks to the sophisticated uplink truck that tailed about a mile behind Bloom and the Third Infantry Division. The vehicle, outfitted for desert wear and tear, transmits over a broader bandwidth than a conventional satellite phone, thus offering crisper images.

The technology has been used on cruise ships before, said Stacy Brady, the network's head of news operations, but never on a truck traveling under rugged battle conditions. "We didn't know if our shocks would keep up," she said.

Separately, five of the network's correspondents in the Gulf are using a new videophone that is smaller, lighter and clearer than the versions employed just 18 months ago in Afghanistan. The new phones weigh about 140 pounds and fit into two suitcases. They were developed in part by Raytheon Corp., the company that developed the Patriot anti-missile system.

The tankcam is but the latest in a long line of new technologies that have been employed during wartime. During the Civil War, the telegraph relayed news with unprecedented speed and still photography provided images for the first time. World War I brought in widespread use of newsreels, and radio matured as a reporting medium during World War II. During Vietnam -- dubbed "the living room war" -- people at home saw the fighting on TV for the first time, albeit at a distance and often several days after the fact.

The ability to see the battlefield for the first time as soldiers move across it has the advantage of immediacy, but raises new professional and ethical questions, says Bob Steele, director of the ethics program at the Poynter Institute, a school for journalists.

"What TV does so well is to take viewers to places they'd never be able to go and where we need to be," he says. "If we're to be informed citizens, if we're to really understand the heroism and horror of war, then we should be able to get as much access to the battlefield as possible."

But instantaneous access brings its own problems. What happens, Steele asks, if a tankcam is watching as a military vehicle hits a land mine or if a convoy comes under sudden artillery assault? Given the unpredictable nature of the battlefield, should viewers be exposed to live carnage?

In other words, because the networks can show it, does that mean they should?

"We shouldn't sanitize [warfare], but we should use a tone and put it in a context that is meaningful," says Steele. "Newspapers put the picture of the dead and wounded on the inside page, based on the idea that the reader has to be prepared for what he's about to see. It's the same reason why the anchorman introduces a graphic piece of footage by saying, 'These images may be disturbing to our viewers.' "

Relaying live pictures of the battlefield also raises a military concern: Can such pictures betray the location of advancing troops? While military officials can order media organizations to stop transmissions if they believe doing so will ensure "operational security," there isn't much agreement over what this term means or under precisely what circumstances it will be applied.

"If you or I had to decide what compromises operational security, I'm sure we would disagree," said CNN's Kross.

The issue was momentarily raised Thursday night by CNN's live pictures from the front. The network's military analyst, retired Gen. Wesley Clark, pooh-poohed anchor Aaron Brown's suggestion that the Iraqis could be monitoring CNN's coverage of the troops' movement. Given the vast and featureless landscape, Clark said it wouldn't matter much -- this time.

NBC's David Bloom presented an endless moonscape."Very powerful and a little eerie" is how CNN's Kathryn Kross describes images that cutting-edge technology makes possible from the war front.