The media couldn't have made a bigger pig's ear of the white phosphorus story. So, before moving on to the new revelations from Falluja, I would like to try to clear up the old ones. There is no hard evidence that white phosphorus was used against civilians. The claim was made in a documentary broadcast on the Italian network RAI, called Falluja: the Hidden Massacre. It claimed that the corpses in the pictures it ran "showed strange injuries, some burnt to the bone, others with skin hanging from their flesh ... The faces have literally melted away, just like other parts of the body. The clothes are strangely intact." These assertions were supported by a human-rights advocate who, it said, possessed "a biology degree".I, too, possess a biology degree, and I am as well qualified to determine someone's cause of death as I am to perform open-heart surgery. So I asked Chris Milroy, professor of forensic pathology at the University of Sheffield, to watch the film. He reported that "nothing indicates to me that the bodies have been burnt". They had turned black and lost their skin "through decomposition". We don't yet know how these people died.But there is hard evidence that white phosphorus was deployed as a weapon against combatants in Falluja. As this column revealed last Tuesday, US infantry officers confessed that they had used it to flush out insurgents. A Pentagon spokesman told the BBC that white phosphorus "was used as an incendiary weapon against enemy combatants". He claimed "it is not a chemical weapon. They are not outlawed or illegal." This denial has been accepted by most of the mainstream media. UN conventions, the Times said, "ban its use on civilian but not military targets". But the word "civilian" does not occur in the chemical weapons convention. The use of the toxic properties of a chemical as a weapon is illegal, whoever the target is.The Pentagon argues that white phosphorus burns people, rather than poisoning them, and is covered only by the protocol on incendiary weapons, which the US has not signed. But white phosphorus is both incendiary and toxic. The gas it produces attacks the mucous membranes, the eyes and the lungs. As Peter Kaiser of the Organisation for the Prohibition of Chemical Weapons told the BBC last week: "If ... the toxic properties of white phosphorus, the caustic properties, are specifically intended to be used as a weapon, that of course is prohibited, because ... any chemicals used against humans or animals that cause harm or death through the toxic properties of the chemical are considered chemical weapons."The US army knows that its use as a weapon is illegal. In the Battle Book, published by the US Command and General Staff College at Fort Leavenworth, Kansas, my correspondent David Traynier found the following sentence: "It is against the law of land warfare to employ WP against personnel targets."Last night the blogger Gabriele Zamparini found a declassified document from the US department of defence, dated April 1991, and titled "Possible use of phosphorus chemical". "During the brutal crackdown that followed the Kurdish uprising," it alleges, "Iraqi forces loyal to President Saddam may have possibly used white phosphorus (WP) chemical weapons against Kurdish rebels and the populace in Erbil ... and Dohuk provinces, Iraq. The WP chemical was delivered by artillery rounds and helicopter gunships ... These reports of possible WP chemical weapon attacks spread quickly ... hundreds of thousands of Kurds fled from these two areas." The Pentagon is in no doubt, in other words, that white phosphorus is an illegal chemical weapon.The insurgents, of course, would be just as dead today if they were killed by other means. So does it matter if chemical weapons were mixed with other munitions? It does. Anyone who has seen those photos of the lines of blind veterans at the remembrance services for the first world war will surely understand the point of international law, and the dangers of undermining it.But we shouldn't forget that the use of chemical weapons was a war crime within a war crime within a war crime. Both the invasion of Iraq and the assault on Falluja were illegal acts of aggression. Before attacking the city, the marines stopped men "of fighting age" from leaving. Many women and children stayed: the Guardian's correspondent estimated that between 30,000 and 50,000 civilians were left. The marines treated Falluja as if its only inhabitants were fighters. They levelled thousands of buildings, illegally denied access to the Iraqi Red Crescent and, according to the UN's special rapporteur, used "hunger and deprivation of water as a weapon of war against the civilian population".I have been reading accounts of the assault published in the Marine Corps Gazette. The soldiers appear to have believed everything the US government told them. One article claims that "the absence of civilians meant the marines could employ blast weapons prior to entering houses that had become pillboxes, not homes". Another said that "there were less than 500 civilians remaining in the city". It continued: "The heroics [of the marines] will be the subject of many articles and books ... The real key to this tactical victory rested in the spirit of the warriors who courageously fought the battle. They deserve all of the credit for liberating Falluja."But buried in this hogwash is a grave revelation. An assault weapon the marines were using had been armed with warheads containing "about 35% thermobaric novel explosive (NE) and 65% standard high explosive". They deployed it "to cause the roof to collapse and crush the insurgents fortified inside interior rooms". It was used repeatedly: "The expenditure of explosives clearing houses was enormous."The marines can scarcely deny that they know what these weapons do. An article published in the Gazette in 2000 details the effects of their use by the Russians in Grozny. Thermobaric, or "fuel-air" weapons, it says, form a cloud of volatile gases or finely powdered explosives. "This cloud is then ignited and the subsequent fireball sears the surrounding area while consuming the oxygen in this area. The lack of oxygen creates an enormous overpressure ... Personnel under the cloud are literally crushed to death. Outside the cloud area, the blast wave travels at some 3,000 metres per second ... As a result, a fuel-air explosive can have the effect of a tactical nuclear weapon without residual radiation ... Those personnel caught directly under the aerosol cloud will die from the flame or overpressure. For those on the periphery of the strike, the injuries can be severe. Burns, broken bones, contusions from flying debris and blindness may result. Further, the crushing injuries from the overpressure can create air embolism within blood vessels, concussions, multiple internal haemorrhages in the liver and spleen, collapsed lungs, rupture of the eardrums and displacement of the eyes from their sockets." It is hard to see how you could use these weapons in Falluja without killing civilians.This looks to me like a convincing explanation of the damage done to Falluja, a city in which between 30,000 and 50,000 civilians might have been taking refuge. It could also explain the civilian casualties shown in the film. So the question has now widened: is there any crime the coalition forces have not committed in Iraq? www.monbiot.com