So Christie did something unusual: he sent a classified letter to Defense Secretary Donald Rumsfeld’s office urging the military to be very cautious about where in Iraq it deployed the Stryker. The response? “I was slapped down,” says the straight-talking Christie. “It was: ‘What are we supposed to do with this [letter]?… Are you trying to embarrass somebody?’ "

There may be embarrassment to come. Six months after that exchange, the fighting in Iraq has called into question not only the Stryker’s effectiveness but the Army’s shift toward a lighter, faster infantry. With a record 138 U.S. soldiers dead in April, some inside the Pentagon are asking why the Army spent billions on new wheeled vehicles like the Stryker when commanders in the field are crying out for old-style treaded vehicles–tanks and personnel carriers–that are better protected and armed.

Many soldiers killed and wounded in Iraq were traveling in thin-skinned Humvees, which ride on rubber tires like the Stryker. Meanwhile, thousands of M113 armored personnel carriers, which are treaded and better armed, sit in mothballs around the world, even next door in Kuwait. That reflects an Army bias that has been prevalent since 1999, when the then Army Chief of Staff Gen. Eric Shinseki–who was frustrated by slow-moving U.S. armor in the Balkans–declared his preference for wheels. But treaded personnel carriers can better bear the weight of the big-caliber guns and armor needed to defeat insurgents and defend against IEDs (improvised explosive devices) and rocket-propelled grenades; Strykers are mounted with only machine guns or grenade launchers. (A new version with a 105mm cannon is months away, says General Dynamics, its manufacturer.) And now “tanks and armored personnel carriers are what commanders are looking for,” Capt. Bruce Frame of CENTCOM told NEWSWEEK.

Still, entrenched interests die hard. So eager were some Army brass to push the Stryker, critics say, that they paid three times as much for it as the competing bid and lowered its performance requirements whenever it failed testing. And even though the Stryker is largely untried, Gen. Larry Ellis of Army Forces Command sent a March 30 memo to the chief of staff asking for more money for the program as far ahead as fiscal year 2008-09. More funding for Strykers is so “imperative,” Ellis wrote, that money might have to be diverted from a program to refurbish Bradley fighting vehicles, the armored, treaded carriers that many soldiers see as the star performer in Iraq. That suggestion raised hackles among track advocates inside the Pentagon. Army spokesman Maj. Gary Tallman said last Friday there is “no plan at this time to buy more Strykers.”

Tallman insists the faster, quieter Stryker is performing ably in Iraq, with only two vehicles lost so far. Each has an additional $500,000 worth of armor around it, including ceramic tiles and an unwieldy cage that some liken to a Rube Goldberg device. Still, the Strykers have been kept from most of the heavy fighting, and they don’t seem able to carry the weight of state-of-the-art “reactive armor.” Tallman adds that the Army is still undecided about whether its “future combat system” will be wheeled or treaded. What happens in Iraq, he adds, will “undoubtedly” influence that debate.