In a story Saturday about army tanks, the Army Science Board was incorrectly identified as the Defense Science Board. (Published 11/08/1999)

For half a century, the U.S. Army has built heavier and heavier tanks, figuring that the best way to protect soldiers on a battlefield was to pack more armor and firepower around them.

Now, it's not so sure.

Behind plans announced last month to develop more agile combat vehicles and medium-weight brigades is a decision by the top brass to rethink the question: What's a tank for anyway?

Seemingly straightforward, the question is actually subversive. It could undermine the Army's traditional emphasis on armor, challenge the notion that wars are won in massive land battles with overwhelming firepower, and dissolve the mystique of the cavalry. It also could upset the Army's best-laid budget plans.

The new thinking envisions breaking tanks into their component parts--cannons, sensors, targeting systems and radios--and distributing these elements around the battlefield on wheels or treads, then linking them with a web of electronic signals.

This "distributive approach," as Army planners call it, promises greater speed and flexibility. But it also faces skepticism in the Army's armored ranks, because it represents a radical departure from the traditional notion of a tank as a bulwark of steel that can stand alone on the battlefield.

"The armored community is not comfortable with a light vehicle whose survival depends on moving faster and knowing more about where the enemy is," said Thomas McNaugher, associate director of the Rand Corp.'s Army research center.

There are other hurdles, too, not least of which is the new approach's reliance on futuristic technologies that have yet to be fully developed. Money, as always, remains a problem.

To finance the transformation without additional funds from the White House or Congress, the Army may have to cut back other big-ticket projects--notably, an $11.5 billion effort to build a self-propelled howitzer called the Crusader and a $48 billion program to buy nearly 1,300 Comanche helicopters. Both projects were conceived during the Cold War, when the Army worried about a massive Soviet attack across the plains of Europe.

Nonetheless, the distributive concept has been endorsed in recent weeks by two authoritative groups: the Defense Science Board and a study team commissioned by the Defense Advanced Research Projects Agency (DARPA), the Pentagon's special projects laboratory. It also has the backing of the Army's top two officers--Gen. Eric Shinseki, the chief of staff, and Gen. John Keane, the vice chief--who assumed their jobs last summer.

By capitalizing on advances in electric motors, robotics, electromagnetic guns, lasers, radar-evading "stealth" materials and other technologies, the Army leaders see an opportunity to engineer lighter vehicles and revamp tactics.

"This is the most fundamental change in the Army that I've seen," said Lt. Gen. Paul Kern, the service's senior acquisitions officer.

Looking to build a constituency for lighter vehicles, Shinseki has reached outside the Army to the Marines, who have voiced concerns about their aging artillery, mortars and attack vehicles. The new Marine commandant, Gen. Jim Jones, has expressed interest in working with the Army on replacements.

Driving the search for a new combat vehicle is what some top officers regard as the reduced relevance of the tank. The top-of-the-line M1A2 Abrams has become too heavy, fuel guzzling and hard to maintain for the new operations engaging the Army.

While tanks clearly had a dominant role when the Army was bracing for battle against Soviet troops, U.S. ground forces are being called on nowadays to deploy quickly to remote places to fight, or keep the peace, without support bases.

"Clearly, the mission has changed," said David Whelan, a senior DARPA official. "It's no longer sitting in Germany figuring out how to hold off a Soviet attack through the Fulda Gap."

Since the early 1950s, the weight of the Army's main battle tank has grown from 50 tons to nearly 70, with ever-larger cannons, bigger turrets and thicker armor. So heavy is today's M1A2 that the largest military transport plane can lift only one at a time.

It also consumes immense amounts of gas, now measured in gallons per mile (anywhere from two to six) rather than in miles per gallon. And because no new tank engines have been built since 1992, existing ones require frequent maintenance--currently, a complete refurbishing every 350 to 550 hours.

Army officials started talking to DARPA two years ago about a new combat vehicle. But the effort gained urgency only after NATO's war against Yugoslavia highlighted the U.S. Army's lack of brigades that were light enough to move quickly, yet heavy enough to strike hard.

The need for rapidly deployable units was further reinforced during the East Timor crisis in September. "East Timor is an example of a situation that, had we had light, agile forces, we probably would have used them," Whelan said.

Under the new plan, the deadline for fielding a light ground combat system has been accelerated from 2025 to 2012. This will require decisions about development and procurement by 2003, Army officials said. As an interim measure, the Army is looking to buy some light armored vehicles already on the market--possibly the Marine LAV, Austrian Pandor or German Wiesel--and use them to create two medium-weight brigades at Fort Lewis, Wash.

Much of the work on the distributive concept is being managed jointly by DARPA and the Army, which has assigned a tank officer, Lt. Col. Marion Van Fosson, as point man. Van Fosson has a doctorate in physics, a fact he prefers not to advertise, worried it will complicate his job persuading fellow tankers.

"It's better if I come across as an armored officer," he said. "I'm trying to emphasize that I don't have all the right ideas. I'm soliciting ideas from everybody."

His own enthusiasm for the new approach was evident as he spoke confidently of a futuristic battlefield of manned combat vehicles teaming with unmanned ones and computer-wielding soldiers able to detect every movement of the enemy.

"We're going to have to change the mind-set," Van Fosson said. "Guys who would stand out there and slug it out toe-to-toe with the enemy in the past will have to learn that their lighter vehicles may not be invincible, but will likely be stealthier and more nimble."

Plans call for several prototypes to be built and tested in the next few years, Van Fosson said. Army officials hope to keep the new vehicle's weight under 20 tons, light enough to be airlifted by C-130 military transports and possibly roll on wheels instead of hard-to-maintain tracks.

The Army has tried to develop a light armored vehicle with anti-tank capabilities before, but without much success. The M551 Sheridan, introduced in the 1960s, had an electronic gun that proved unreliable. The Bradley Fighting Vehicle, which emerged in 1981, was supposed to weigh 15 tons but ended up at 25. And the Armored Gun System, which was ready to enter production several years ago, was killed in a budget crunch.

"If you go back and look at the future of fighting vehicles for the last 30 years, we've been talking about this kind of stuff for a long time," said Col. Dan Kaufman, a professor at the U.S. Military Academy at West Point. "But what we've tended to do is take the most demanding scenario and design the vehicles against it, which has ratcheted up their weight."

CAPTION: ENVISIONING AN AGILE TANK (This graphic was not available)