The latest body blow to U.S. credibility, if such a thing still exists, was a year in coming. And it needn’t have happened at all.

Between Nov. 8 and Nov. 20, 2004, U.S. forces in Iraq conducted Operation Phantom Fury, also known as the Battle of Fallujah. It was a ferocious fight for control of the city of 250,000 just 35 miles west of Baghdad.

Weeks later, a State Department press release criticized “misinformation” in scattered reports by a few overseas media outlets about some of the weapons used at Fallujah, including the flammable chemical white phosphorus. Phosphorus shells, the Dec. 9 release said, were used “very sparingly in Fallujah, for illumination purposes. They were fired into the air to illuminate enemy positions at night, not at enemy fighters.”

This was false.

“Some artillery guns fired white phosphorus rounds that create a screen of fire that cannot be extinguished with water,” the Washington Post had reported from Fallujah during the battle. “Insurgents reported being attacked with a substance that melted their skin, a reaction consistent with white phosphorus burns.” A doctor at a nearby hospital confirmed that “some corpses” of insurgents “were melted.”

Nor was it the first time U.S. forces had used white phosphorus against human targets in Fallujah. During an April 2004 operation that was cut off in midstream on orders from Washington, mortar companies routinely alternated white phosphorus shells with conventional high explosives.

On April 10, Darrin Mortenson of the North County Times (Escondido, Calif.) reported watching troops in a mortar pit, “sending a mixture of burning white phosphorus and high explosives they call ‘shake ‘n’ bake’ into a cluster of buildings where insurgents have been spotted all week.” Mortenson and photographer Hayne Palmour were traveling with Marines from Camp Pendleton.

In the March-April 2005 issue of Field Artillery, a U.S. Army publication, officers who had fought at Fallujah the previous November described artillery and mortar operations, including the use of white phosphorus. It was used, they wrote, to create smoke to mask troop movements and “as a potent psychological weapon against the insurgents in trench lines and spider holes. … We (used) WP to flush them out and HE (high explosives) to take them out.” However, they wrote, it would have been better to save the white phosphorus “for lethal missions.”

Indeed. White phosphorus, as described in the incendiary weapons section of the authoritative globalsecurity.org Web site, ignites spontaneously on contact with air. That chemical reaction generates an intense heat and “painful chemical injuries.” Once particles get into a person’s skin, they rapidly penetrate and dissolve fatty tissues; hence the melting effect. “These weapons are particularly nasty,” according to the Web site, “because white phosphorus continues to burn until it disappears.”

All this was known – notwithstanding the State Department’s false denial of a year ago – when a documentary aired last month on Italy’s RAI television. The Nov. 8 broadcast presented what it said were photographs and testimonial evidence that Iraqi civilians, including women and children, were horribly killed and injured by white phosphorus during the U.S. assault on Fallujah last November.

At this point, a simple truthful explanation from U.S. officials might well have defused the potentially explosive controversy. That is not, however, how the Bush administration responded.

U.S. embassies overseas issued carefully worded statements implying that white phosphorus had been used only for smoke and illumination, not against people. A few days later, under the subheading “United States did not use phosphorus weapons,” a somewhat narrower Pentagon statement declared that “we did not use white phosphorus against civilians.”

It took a week for a Pentagon spokesman, Lt. Col. Barry Venable, to finally acknowledge to the BBC that the U.S. had used white phosphorus “as an incendiary weapon against enemy combatants.” Still, he insisted, at no time did U.S. forces target civilians.

The idea that U.S. forces would deliberately target civilians with white phosphorus or anything else is, of course, nonsense. But the Pentagon’s shifting explanations – on top of a five-year pattern of evasions, half-truths and false denials by the Bush administration – have given the world reason to doubt what should be an obvious truth.

And the government’s legal hair-splitting and double-speak only makes it worse:

Is white phosphorus a chemical weapon? Depends on your interpretation of “toxic properties” as defined in the international Chemical Weapons Convention. But didn’t the U.S. call it a chemical weapon when we heard Saddam used it on the Kurds in 1991? So what? Is it an incendiary weapon? Not if it’s used for smoke and illumination. But the U.S. used it as an incendiary. Did we? The Pentagon finally admitted it did in Fallujah. And Protocol III on incendiary weapons of the Convention on Certain Conventional Weapons prohibits its use in a “concentration of civilians.” The U.S. never ratified Protocol III.

This dithering over definitions is sick and demeaning. Does the United States really need to mount a defense based on sleazy parsing of words, phrases and technicalities?

Americans by nature are an optimistic and fair-minded people; it’s to our credit that trust dies hard. But this administration has long since relinquished any legitimate claim to the benefit of the doubt. It doesn’t matter whether this is the result of malevolence, incompetence or an ad hoc blend of both. Because of the Bush administration, what America says to the world is no longer regarded as credible. It could take a generation to repair the damage.