Aware of the debilitating effect drugs had on the morale and effectiveness of GIs in the Vietnam War, the authorities are attempting to stifle a repeat in Iraq.

Aside from random urine tests and barrack room searches, commanders have asked their troops to inform on colleagues.

In the past month a soldier has been arrested for selling cocaine and two per cent of the troops from one brigade have been charged with drug and alcohol abuse.

According to US army figures, out of the 4,000 men of the 256th Brigade Combat Team, 53 faced alcohol-related charges and 48 were charged with drug offences.

Since the overthrow of Saddam's regime the borders that have been so porous for insurgents have been equally open for heroin and hash smugglers from Afghanistan and Iran providing a cheap market for troops. With colleagues being killed or wounded on a daily basis, some US soldiers have turned to drugs to escape the horrors of fighting insurgents.

In one case, according to Stars and Stripes, the in-house US forces newspaper, Sgt Michael Boudreaux was found with drugs, four bottles of whiskey and 22 videos of Iraqi pornography. He received a seven month confinement, was demoted to private and given a bad conduct discharge.

In another case, Pte Emily Hamilton told a court martial that she used a hashish pipe belonging to a colleague because "it helped me go right to sleep". She was given a year's confinement and a bad conduct discharge.

"Some of these young soldiers just can't handle the stress," said Capt Christopher Krafchek, a military defence lawyer.

The majority of drug-users are in their teens or early 20s, and sometimes get their drugs from local Iraqis while on patrol in Baghdad.

Troops caught in possession of illegal substances are either jailed, demoted or discharged from the forces.