COMPETING ideologies have so thoroughly colored the question of how well the Patriot missile-defense system performed in the Persian Gulf war that one approaches the issue today expecting to be misled.
After the war, President Bush, Defense Secretary Cheney, and other true believers in strategic defense exaggerated Patriot's success in intercepting Iraqi Scuds in order to bolster the case for the Strategic Defense Initiative (SDI).
Ideological opponents of SDI later rallied to the banner of Rep. John Conyers (D) of Michigan and his Government Operations Committee. Their anti-Patriot case included television footage supposedly showing Patriot misses. But the footage was shot at relatively slow speeds, which made hits look as though they detonated well behind the Patriot.
In truth, we are unlikely ever to know with precision the percentage of Iraqi modified, long-range Scuds (called Al Husseins) whose warheads were destroyed or that were pushed significantly off course by Patriot interceptors.
The Army claims that 70 percent of the Iraqi missiles headed for Saudi Arabia and 40 percent of those headed for Israel were successfully engaged. But corroborating evidence, such as digital data recordings or Scud debris showing damage from exploding Patriot pellets, is generally lacking.
The Army's case is largely circumstantial. If Patriot radar detected an Iraqi missile on a course likely to hit, say Daharan; if Patriots were fired, traveled on their intended trajectory, and detonated; and if little or no Al Hussein warhead damage resulted, the Army infers the Patriot successfully intercepted its target. What else could account for the harmless result?
Israeli military analyst Reuven Pedatzur, highly critical of Patriot performance, offered the Conyers committee one explanation - the tendency of the Al Hussein to break up in flight. If the cables and generators needed to activate a missile's timed arming mechanism disintegrated, the warhead would not have exploded whether a Patriot hit or missed.
Still, there is much that mitigates the Patriot's problematic wartime performance. This was, after all, a missile designed for defense against aircraft, and modified to provide some protection against short-range ballistic missiles. Patriot's limited speed and range made it more useful defending a specific point - a port or airfield - than an entire city.
Patriot hardware and software, as well as the tactics for its use, were repeatedly modified during the war to prevent its chasing Scud debris rather than warheads and to otherwise improve its performance.
In one tragic example, Israeli crews discovered that the Patriot computer's ability to identify the "range gate" in which the Al Hussein should be intercepted deteriorated the longer the system was kept running. New software to fix the problem arrived in Saudi Arabia Feb. 26, 1991, one day after the system's computer, having run for 50 consecutive hours, failed to detect the Al Hussein that smashed into the military barracks in Daharan, killing 28 Americans.
ONCE ideology is put aside, Patriot performance offers some important lessons for the future.
First, Patriot itself must be improved to enable it to intercept enemy missiles at greater range and altitude, to avoid debris damage to defended areas.
Second, the warhead must be made more lethal against enemy warheads.
Third, a layered defense is better than sole reliance on low-altitude interceptors. Israeli and US systems now in development offer the promise of high-altitude interception with a system like Patriot used to chase down those missiles that breach the outer layer.
Fourth, a sophisticated offense will provide serious problems for any defense. By breaking up in flight, the Al Hussein lost all accuracy. But by inadvertently providing decoys, it befuddled a number of Patriot interceptors. Had the Iraqis fired their missiles in barrages rather than singly, it is likely the Patriot batteries would have been overwhelmed.
Finally, even if the Patriot had equaled or exceeded the administration's early claims, had they been confronting Scuds armed with nuclear warheads the results would have been a horrifying disaster for both Israel and Saudi Arabia.
This suggests modest goals for a system designed to defend against strategic nuclear missiles. Only against a mere handful of such missiles can a defense system fully protect citizens.
By exaggerating the performance of Patriot, the US could well buy into too ambitious a missile-defense system. By demeaning that performance, however, a useful future hedge against accident or the act of a madman could be missed.