When an Italian TV network ran a report earlier this month alleging that the United States had used white phosphorus shells on civilians in Fallujah, Iraq, we noted that the Pentagon had a history of backtracking on its denials of related claims.

In the early days of the Iraq war, there were reports that U.S. troops had used napalm during their march to Baghdad. The Pentagon denied that charge but then admitted that troops had, in fact, used a "napalm-like" substance in Mark-77 bombs. When accusations about the use of white phosphorus in Fallujah first arose last year, the United States denied those charges too, insisting that it had used phosphorus shells "very sparingly in Fallujah" but only for "illumination purposes."

The Pentagon made that same claim in response to the Italian TV report, but now, as the New York Times reports today, it's backtracking once again. Confronted with what the Times calls "firsthand accounts" by two Americans officers who say that white phosphorus shells were aimed at insurgent targets in Fallujah, the Pentagon is now acknowledging that troops directed white phosphorus at insurgents. "It's perfectly legitimate to use this stuff against enemy combatants," Lt. Col. Barry Venable tells the Times. Venable couldn't rule out the possibility that some civilians were hit by white phosphorus, too.

Slippery slope or sloppy spin? It's hard to say. Weapons expert John Pike tells the Times that "stupidity and incompetence" by U.S. officials responsible for communicating with the public have allowed questions to be raised where there shouldn't be any. "The story most people around the world have is that the Americans are up to their old tricks -- committing atrocities and lying about it," Pike says. "And that's completely incorrect."

But when you've started a war based on false claims about the threat of WMD, people expect you to meet a pretty high standard of care yourself. Daryl Kimball, the director of a nonprofit group that researches nuclear issues, tells the Times that it might be time for an independent investigation into whether the use of white phosphorus in Iraq complied with international law. "There are legitimate questions that need to be asked," he says. Some war critics think they've already got the answers. As Tribune Media Services columnist Robert Koehler writes, "Turns out the United States doesn't use chemical weapons the same way it doesn't do torture."