Rana Al-Aiouby was risking her life delivering essential medicine to the wounded in the Iraqi city of Fallujah when she witnessed first-hand the effect of chemical weapons deployment by US troops. Despite their prohibition under several international treaties and by the Geneva conventions, white phosphorus and a napalm derivative were used without discrimination on the civilian population of a city the size of Edinburgh throughout 2004.

"I noticed something in the garden and it was a body but I couldn't really recognise it, and it looked really bad - it was a body with the colour green, and I have never seen this in all my life, and my work is dealing with dead bodies."

Few people know about the crimes committed during the two sieges of Fallujah - Operation Vigilant Resolve, launched three years ago tomorrow, and Operation Phantom Fury, in the following November - as a result of which 200,000 people became refugees. There are no official figures for civilian deaths.

In the face of repeated independent verification, US forces have now acknowledged the use of chemical weapons, and yet there remains no sustained international outcry and no official response (let alone condemnation) from any government or the United Nations. The US has overthrown a regime while supposedly searching for phantom weapons of mass destruction, only to use such weapons on the newly "liberated" civilian population. The cold hypocrisy of such actions is outweighed only by its extravagant viciousness.

Seventy articles of the Geneva conventions were breached in the two separate months of siege warfare. Despite calls to abolish the conventions by the past and present Conservative leaders Michael Howard and David Cameron among others, they remain an essential bulwark against the bullying tactics of the powerful, and a poignant index of the increasing impunity of the neo-colonial project. Their ethos is that the innocent, the weak, the defeated and the injured be afforded all the protection possible in times of conflict. The ethos of the US government is that the weak and innocent are a hindrance to the acquisition of power and, occasionally, an opportunity for the expansion of profit.

In writing my play Fallujah, which weaves together eye-witness accounts from Rana and many others present during these attacks, what astonished me was the symmetry between the testimony of American soldiers and that of their victims: "Yeah, we napalmed those bridges," said Colonel Randolph Alles, of Marine Air Group 11, in an interview with James Crawley of the San Diego Union-Tribune. "The generals love napalm." The guys on the ground no longer bother dissembling, so confident are their masters that protest, should it happen, will be muted and ineffectual.

The rhetoric of impotence so prevalent in the west has been too effective and we are too weary to be surprised, let alone act. As with the proposed abolition of the Geneva conventions, what is in evidence is a kind of fatigue, a sense that ethical action is just too troublesome in our complicated and distracted world. Yet the irony is that as members of a privileged European society, with unparalleled material wealth, leisure time, communications technology and intellectual opportunity, we are in an unprecedented position of influence, no longer dependent on the ballot and the wallet to exercise protest. We have never been better placed or equipped as individuals to make an impact on the world; this is obvious from the huge changes we are making to the environment. All the people I interviewed for Fallujah and whose testimony is reproduced verbatim, from generals to clerics to Iraqi civilians, acknowledged this. We are all participants now.

Many of the Iraqis I have met repeated the same slogan: "Fallujah now is Iraq, and Iraq is Fallujah." Three years on, people have returned to what remains of their homes, but life is no less dangerous. Spot searches, evictions and sudden attacks are common, the city has no real infrastructure, little clean water and almost no healthcare, and factional warfare is a daily occurrence. It is still very difficult for aid to reach the city or for observers to see just how hard life is for residents.

What is certain is that the damage done has not been repaired and no reparation has been forthcoming, despite promises from the Iraqi interim authorities. The city is in a chaotic state, and many people feel that once again they have been forgotten. The atrocities of three years ago have become emblematic of a nation's suffering; unless we respond with compassion the emblem will harden into a symbol of resistance and reaction, and we will reap the whirlwind sooner than we care to think.

· Jonathan Holmes is a writer, director and academic; his play Fallujah opens at the Old Truman Brewery, London, on May 1

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