Last January, these memories became too much for this veteran of the war in Iraq. Informed his unit was about to return, he told his commanders he wanted out and applied to be considered a conscientious objector. The Army refused and charged him with desertion. Last week, his case - which carries a penalty of up to seven years' imprisonment - started before a military judge at Fort Stewart in Georgia.

"If I am sincere in what I say and there's consequences because of my actions, I am prepared to stand up and take it," Sgt Benderman said. "If I have to go to prison because I don't want to kill anybody, so be it."

The case of Sgt Benderman and those of others like him has focused attention on the thousands of US troops who have gone Awol (Absent Without Leave) since the start of President George Bush's so-called war on terror. The most recent Pentagon figures suggest there are 5,133 troops missing from duty. Of these 2,376 are sought by the Army, 1,410 by the Navy, 1,297 by the Marines and 50 by the Air Force. Some have been missing for decades.

But campaigners say the true figure could be far higher. Staff who run a volunteer hotline to help desperate soldiers and recruits who want to get out, say the number of calls has increased by 50 per cent since 9/11. Last year alone, the GI Rights Hotline took more than 30,000 calls. At present, the hotline gets 3,000 calls a month and the volunteers say that by the time a soldier or recruit dials the help-line they have almost always made up their mind to get out by one means or another.

"People are calling us because there is a real problem," said Robert Dove, a Quaker who works in the Boston office of the American Friends Service Committee, one of several volunteer groups that have operated the hotline since 1995. "We do not profess to be lawyers or therapists but we do provide both types of support."

The people calling the hotline range from veterans such as Sgt Benderman to recruits such as Jeremiah Adler, an idealistic 18-year-old from Portland, Oregon, who joined the Army believing he could help change its culture. Within days of arriving for his basic training at Fort Benning, Georgia, he realised he had made a mistake and said the Army simply wanted to turn him into a "ruthless, cold-blooded killer".

Mr Adler begged to be sent home and even pretended to be gay to be discharged. Eventually, he and another recruit fled in the night and rang the hotline, which advised him to turn himself in to avoid court-martial. He will now be given an "other than honourable discharge".

From southern Germany where he is on holiday before starting college in the autumn, Mr Adler told The Independent: "It was obviously a horrible experience but now I'm glad I went through it. I was expecting to meet a whole lot of different types of people; some had noble reasons. I also met a lot of people who [wanted] to kill Arabs." In one letter home to his family, Mr Adler wrote that when he arrived he was horrified by the things he heard other recruits talking about, things that in civilian life would result in someone being treated as an outcast. In another letter he said he could hear other recruits crying at night. "You can hear people trying to make sure no one hears them cry under their covers," he wrote.

Mr Adler now provides advice to other recruits who have decided the military is not for them. "When people contact me I tell them go Awol; it's the quickest way to get out," he said. "I was told I would be facing 20 years hard labour at Fort Leavenworth [military prison] because that is what the sergeant will tell you. I learnt that was not the case."

Jeremy Hinzman, 26, a reservist with the 82nd Airborne Division who served in Afghan-istan, decided to go Awol after his unit was ordered to Iraq. He took his wife and child and fled to Canada, hoping to be welcomed, as were the 50,000 or so young Americans who sought refuge north of the border to avoid the Vietnam war.

But in March he was refused refugee status by the Canadian Immigration and Refugee Board. Mr Hinzman, who is appealing the decision, told the hearing: "We were told that we would be going to Iraq to jack up some terrorists. We were told it was a new kind of war, that these were evil people and they had to be dealt with ... We were told to consider all Arabs as potential terrorists ... to foster an attitude of hatred that gets your blood boiling."

Campaigners say recruits who decide they want to leave the military are the most vulnerable to pressure from sergeants and officers who try to force them to stay. Some are told they will go to jail, others are told they will never be able to get a job if they receive a "less than honourable discharge", they say. They also face intense peer pressure and abuse, as they try to get out and after they manage to do so.

Campaigners have also drawn attention to the often scurrilous tactics used by US military recruiters, who for three months have failed to meet their targets for recruits. After several cases where recruiters had illegally covered up recruits' criminal and medical records, threatened one prospect with jail for failing to meet an appointment and provided another with laxatives to help him lose weight and pass a physical, the Pentagon is halting all recruiting on 20 May for a day of retraining.

Senior commanders have said the present recruiting environment - with the war in Iraq having cost the lives of more than 1,600 servicemen and women and the economy able to offer other jobs - is their most difficult. Despite this, the Pentagon insists it is committed to finding recruits in a fair and transparent process. Colonel Joseph Curtin, an Army spokesman, said the retraining day would give recruiters time to "focus on how they can do a very tough mission without violating good order and discipline".

JE McNeil, who heads the Centre for Conscience and War in Washington DC, a Christian group whose members also staff the GI Rights Hotline, said many troops she spoke with had been lied to by recruiters. "I had an 18-year-old who was told he did not have to serve in Iraq. 'I was told I'd get a job where I would not be sent', he told me," said Ms McNeill, a lawyer. "He was recruited to be an military policeman. They are the people they are sending to Iraq. People all the time are told [by recruiters] 'I can get you a job where you will not have to go to war'."

Campaigners say that despite pressure on unhappy recruits exerted in the barracks and the insults they will likely face, if a recruit follows the correct legal procedure they can usually get out of the military. One of the biggest hurdles for those who want out is obtaining the correct information on how best to proceed. Usually, the advice to those on the run is to turn themselves in. After 30 days of being Awol a serviceman is considered a deserter, and a warrant is issued for his arrest. At that point, he can be returned to his unit, court-martialled or given jail time or - and this is more often than not the outcome for recruits - they will be given a non-judicial punishment and an less-than-honourable discharge. Volunteers say usually the military is more inclined to let go those who have had the least training and are the least specialised. But an experienced Air Force pilot, for instance, in whom the military has invested hundreds of thousands of dollars, could face a much more difficult time in getting out. "The most important thing we do is listen and not lie," Ms McNeil said. "Sometimes I tell people there is nothing they can do. I don't enjoy saying it but some times that is it."

Kevin Benderman is anything but a raw recruit. He joined the US Army in 1987, served in the Gulf War and received an honourable discharge in 1991. He rejoined in 2000 and served during the invasion of Iraq with the 4th Infantry Division. He says what he saw there left him morally opposed to returning to war applied to be a CO. The military says that on 10 January he failed to show up when his unit was to ship out.

Last week, at Fort Stewart, a military judge started a so-called Article 32 hearing to decide whether there is sufficient evidence for a full court-martial of Sgt Benderman. The proceedings recommence on 26 May. Sgt Benderman's wife, Monica, who had been heavily involved in organising his defence, said: "A lot of what they are saying about Kevin is not true. He never went Awol and was never a deserter. He is staying strong. I am proud of him. He has had a lot thrown at him over the past three days. If you consider what he has gone through he is doing very well. If people cannot see he is genuine, then they are not looking at him."

The Pentagon says it does not keep records of how many try to desert each year. A spokeswoman, Lieutenant Colonel Ellen Krenke, said the running rally had declined since 9/11 from 8,396 to the present total of 5,133. She added: "The vast majority of those who desert do so because they have committed some criminal act, not for political or conscientious objector purposes."