Some generals recognized the limitation of tanks during the first hours of the Yom Kippur War in 1973. Egyptian combat teams equipped with Soviet-made shoulder-fired missiles destroyed 165 of Israel's 265 first-echelon tanks, quickly disproving the maxim that it takes a tank to kill a tank. A quarter century later, NATO's experience in Kosovo sealed the issue for any laggers. While U.S. Apache helicopters, set to attack tanks, eventually got to their staging area in Albania, American tanks were a no-show. The Abrams tanks that in 1991 brought the Persian Gulf War to a close in 100 hours had, for the most part, traveled to the Mideast by boat. In Kosovo, however, these 70-ton tanks were too heavy to arrive in time. During airlifts, only one can fit inside a C-5 or C-17 at a time.

Even if Abrams tanks had been prepositioned, military strategists say, it is questionable if their presence would have made much of a difference in the outcome of the conflict. Fighting in Eastern European cities is as different from open desert warfare as it gets. The heavy armor that made the Abrams so formidable a deterrent against a Soviet tank invasion of Western Europe during the Cold War years had become a strategic liability.

The size of the tanks was more than could be handled by the crumbling infrastructure linking the remains of what had been Yugoslavia. For Pentagon planners, the truth was inescapable. The U.S. Army, the world's only deployable army, was in effect muscle-bound. Its most powerful land weapon was too big to get to a fight.

On Oct. 12, 1999, the Department of Defense announced a historic break with its past. It would attempt to restructure the Army so that

it could put a ready-to-fight combat brigade anywhere in the world within 96 hours.

And that was only the start. Within 120 hours a full division--that's about 15,000 soldiers--could be in harm's way. Within 30 days, five divisions could be fighting. By way of comparison, it took the United States a full 185 days to prepare for the 100-hour ground war in the Gulf.

As startling as the Army's transformation program would be, the speed with which this change would take place would be greater. "We will begin to immediately transform the entire Army into a more dominant and strategically responsive force," says Gen. Eric K. Shinseki, chief of staff of the Army. To accomplish this, Shinseki ordered that the new IBCT be equipped with off-the-shelf hardware. And so, a mere 10 weeks after the announcement of the Army's reorganization, POPULAR MECHANICS is standing on the frosty Baum Firing Range at the U.S. Army Armor Center at Fort Knox, Ky. We have been invited to watch the Pentagon's "platform performance demonstration (PPD)," a head-to-head test of 35 combat vehicles from seven countries.

Pushing the airbrake and dropping the transmission into the automatic two-to-five speed range, we accelerate the 22,000-pound Dragoon 4x4 Armored Troop Carrier across the deserted Hurley Tank Motor Park. From his right-seat position, Jeff Cunningham of General Dynamics Land Systems explains that we are driving the same vehicle that's currently used by the Venezuelan army and Turkish National Police. American soldiers inside a French Vehicle de l'Avant Blinde 6x6 Armored Personnel Carrier are negotiating an urban combat zone that resembles a Kosovar village. In the weeks that follow, Pentagon planners will use the results of the PPD to help define a future fighting machine.