That there was always some exaggeration regarding the effectiveness of US hardware in the war has been known for some time. The performance of the Patriot anti-missile system, lauded during the war, has come under particularly scrutiny.
But this report, which the Pentagon until the last had been trying to suppress, gives new and startling detail about what it terms a "pattern of overstatement" by defence officials and the manufacturers of the systems in assessing their effectiveness both to journalists and elected representatives.
Prepared by the General Accounting Office (GAO), which is the investigating body of the US Congress, the document will cast a long shadow when Congress considers future spending for arms programmes with price-tags matched only in extravagance by the sci-fi claims attached to them.
American taxpayers will be especially surprised to hear a central conclusion of the report that there was "no apparent link between the cost of aircraft and munitions and their performance in [Operation] Desert Storm". The super-expensive F-117 stealth fighter and the much more basic A-10 aircraft both managed "100 per cent survivability" when flown at night.
While the Pentagon claimed that laser-guided bombs dropped by the F-117 aircraft struck their targets 80 per cent of the time, the report says that in fact a third of those hits could not be corroborated. "Desert Storm data do not fully support claims for the F-117's accuracy," the report concludes. Indeed, the real hit rate may have been as low as 41 per cent.
The GAO debunks assertions that on the first night of Desert Storm, the Lockheed F-117s struck 37 crucial targets in Iraq. Instead, the report says, aircraft from various coalition countries, Britain included, hit just 21 of those 37 targets and the "F-117s missed 40 per cent of their air defence targets".
The Tomahawk cruise missiles also apparently did a less brilliant job than at first asserted. On the Pentagon's insistence, however, the actual success rate of the Tomahawks remains classified. Thus the report says "subsequent intensive analysis shows that the hit rate was (text deleted) per cent". Whatever that figure is, it is "less than generally perceived", it adds.
The report also overturns the Pentagon's famous "one target, one bomb" for its laser-guided bombs, suggesting that it took between four and 10 bombs to attack targets such as bridges.
John Dingell, a US representative from Michigan, said the document showed a "pattern of overstated, misleading, inconsistent or unverifiable claims" and exposed important information about the effectiveness of highly expensive systems that "until now had been withheld from the taxpayer".