Under the headline, “Some of the lessons learned during the battle for Fallujah”, the US Marine Corps Gazette is clear about the practical uses of phosphorus, which ignites on exposure to oxygen and produces an intense heat: “Used when contact is made in a house and the enemy must be burned out.”

Guidance like this, in the Marines’ own journal in September, lay behind the Pentagon’s abandonment on Tuesday night of its long-held position that white phosphorus was used “very sparingly” during the battle of Fallujah last year, and only for illumination.

A US government website had previously insisted that phosphorus shells were merely “fired into the air to illuminate enemy positions at night, not at enemy fighters”. The Pentagon now admits that phosphorus was indeed “used as an incendiary weapon against enemy combatants” — although not against civilians. In London Robert Tuttle, the US Ambassador, who on Tuesday rebutted reports that American forces used phosphorus as a weapon, told The Times: “We did the best we could with the information we had, but we regret that it was not totally accurate.”

Washington’s new position is that phosphorus is “not a chemical weapon” and “not outlawed or illegal”. The Organisation for the Prohibition of Chemical Weapons, which polices the 1993 convention prohibiting chemical weapons, accepts that position. Its spokesman said that phosphorus was covered instead by the 1980 Convention on Prohibitions or Restrictions on the Use of Certain Conventional Weapons Which May be Deemed to be Excessively Injurious or to Have Indiscriminate Effects.

Although the US ratified parts of this convention in 1995, it has failed to enact Protocol III, which bans the use of incendiary weapons against civilian populations and in air attacks against military forces in civilian areas. They can be used against military targets separate from civilian positions.

The row, which began with claims in an Italian television documentary that accused the US military of using phosphorus on women and children, led Britain to deny yesterday that British forces had used the substance on civilians or enemy combatants. John Reid, the Defence Secretary, said that it was used “to produce a smokescreen to protect our troops.”

A British military source said: “There’s nothing to stop us, but it’s just that we have a different doctrine and it’s not a tactic we turn to.”

Calls for a review of the use of phosphorus were led yesterday by Doug Henderson, the former Armed Forces Minister, who said: “You cannot say you are going to invade a country to find chemical weapons and prevent them being used and then admit that you have used chemical weapons yourself.”

In Marine Corps Gazette Volume 89, four Marines, co- authors of an article on lessons from Fallujah, argue that the improvised white phosphorus bomb, made with a 60mm or 81mm white phosphorus mortar round, “was developed in response to the enemy’s tactics and has been proven to work”.

They add: “Marines were killed on the field of battle developing these techniques. It is the duty of every Marine infantryman to ensure that these lessons do not die.”

Times Recommends

• 'Great Schlep' may seal deal for Obama
• Hindu 'storm troopers' flex their muscles
• Ahtisaari: deserved reward for (failed) plan