UNTIL recently a small piece of First World War history had been left buried.

Though the image of the graceful, compassionate nurse tending a broken soldier has been popular throughout the century, we have known very little about these women, 24,000 of whom served between 1914 and 1918. Their part in the war had, until lately, mostly slipped from memory. Their sufferings and injuries, the horrors they witnessed and the shell shock some experienced, were little talked about.

But all that is changing. A small number of academics are examining these women's stories. A drama series, The Crimson Field, based around nurses and volunteers in a field hospital in northern France, begins tonight on BBC One, and Edinburgh University historian Yvonne McEwen is campaigning for a memorial to be built in the nurses' honour.

"People talk about the casualties of war," says McEwen, author of A Long Way To Tipperary: British And Irish Nurses In The Great War, "but nobody ever thinks about who it is that cares for the casualties of war, and whether the carers could become casualties themselves." McEwen believes the nurses were treated as both "invisible and invincible" by the culture of the time.

"Nursing leadership," writes McEwen in her book, "made no attempt to record the nurses' wartime endeavours and sacrifices. There was no roll of honour for those who gave their lives so generously. An incomplete list of names was all that remained in the nursing archives and the deaths of 378 nurses went unrecorded."

There were, she adds, few, if any, commemorations. But McEwen is changing that with her campaign to set up a memorial for the nurses who died in both world wars at the National Memorial Arboretum in Staffordshire. Some 1700 of these victims are known, though, she says, there are 500 more whose stories are being investigated and, "almost on a monthly basis other names arrive".

Dig deep enough into the diaries and letters left by nurses, and details start to emerge of death, trauma and injury. From May 15 to June 1, 1918, base hospitals on the north coast of France were bombed seven times. Five nurses were killed and 11 injured. One described how 89 nurses shelled out of casualty clearing stations (makeshift hospitals near the frontline) arrived at her base hospital. "They had the most awful experience. One English sister was killed instantaneously … The shell burst just outside the tent - a piece of shrapnel … piercing the subclavian artery - she died 10 minutes later … At the Canadian Casualty Station a sister lost her right eye." She also notes that "several of the sisters had to be evacuated because of shell shock".

The conditions were tough and there were physical risks for nurses as well as soldiers. Some contracted diseases - malaria, dysentery, ===enteritis - others were hit in aerial bombing or injured when a hospital ship was torpedoed. "All these things happened," says McEwen, "and nobody gave a thought to them. It was what was expected and it was

noble. And that's fine, but they were just invisible from the text in history."

McEwen's interest in the subject was inspired by her grandfather, who sustained near-fatal injuries in the Battle of the Somme. "I wanted to know the kind of women that looked after him. He was in a military hospital in Dublin and then in 13 different government institutions. He was treated for shell-shock at Kingston House war hospital in Edinburgh - the only hospital established in Scotland at the time to treat shell-shocked sailors and soldiers." (Craiglockhart, where Wilfred Owen and Siegfried Sassoon recovered, treated only officers.)

But the impact of war on the nurses who served in the British and Dominion Forces was not just a matter of lives lost or even injuries. There was the psychological assault of prolonged contact with suffering and horrifying dismemberment. One sister, nursing gas victims, noted: "I have seen things here that I shall never be able to forget ... I have felt as though I was living through a hideous nightmare, with visions of choking men, with blackened burned faces, being held down by orderlies and attached to their beds to prevent them throwing themselves out of the window in their last struggles for breath."

War pension records reveal the list of disabilities affecting former nurses included tuberculosis, rheumatoid disease, cardiac conditions and "neurasthenia", a term for post-traumatic mental breakdown that was sometimes also called shell-shock. Some nurses were actually sent home for being "shell-shocked" - though, as McEwen points out, it's not clear what this meant. "Was it a blanket term for people falling apart?" she wonders. "There were so many manifestations of psychological reaction to war that everyone got classed as shell-shock."

But, she notes, there is no evidence women suffered from it any more than men. "In fact, I'm surprised how stoic the women were." The belief after all at that time was that women were of weaker character than men. "Until 1915 nurses weren't allowed in clearing hospitals because they thought it was too dangerous and far too much strain on a nurse," says McEwen. "But towards the end of 1914 they began to realise they were going to have to have women in casualty clearing stations."

Far from being prone to breaking down, nurses tended to be "formidable". But then, they needed to be."It wouldn't have done to look like they were weak and not coping," says McEwen.

In fact, there were many reasons why women might break down: personal issues relating to their lives back home, the loss of a dear brother or family member, and, of course, the pressure of the environment itself. "I cannot begin to imagine it was like for these nurses," says McEwen, a former trauma nurse who has worked in conflict areas. "Of course they would break down. The fact that so many of them didn't is a marvel."

The Crimson Field focuses on some of the middle-class volunteers recruited by the Red Cross to form the Voluntary Aid Detachment. For many of those untrained young women, the experience was particularly shocking. Among them was Vera Brittain, mother of Baroness Shirley Williams, who later wrote a moving memoir of the period, Testament Of Youth.

Williams has written recently about this episode in the life of her mother and other women. "Thousands of young women from middle-class homes with little experience of domestic work, with not much relevant education and total ignorance of male bodies, volunteered and found themselves pitched into military hospitals ... The image and the conspicuous Red Cross uniforms were romantic but the work itself exhausting, unending and sometimes disgusting."

There were also some independent volunteers, including Scot Mairi Chisholm, one of the two women who became known as "the Madonnas of Pervyse" (a village north of Ypres) when she and her friend Elsie Knocker set up an outpost in a cellar right behind the Belgian frontlines. They got as far forward into the frontlines as any women did in the war. A skilled motorbike racer, Chisholm had been recruited as an ambulance driver after a doctor saw her nipping through the traffic. She was not a nurse, though Knocker was a trained midwife and taught her the basics.

By the end of the war Chisholm had been gas-poisoned, contracted septicaemia and was left with a weak heart: she said it was the result of "humping men on my back". Their war ended in March 1918, when, in a big offensive, the pair were gassed so badly, with mustard and arsenic, they had to be sent home. "If it had been pure mustard we would have been dead, of course," Chisholm recalled in 1976. "But the arsenic has been a bother, definitely, because it did the insides in for quite a long time, the digestive processes."

The nurses' job was made tougher by lack of facilities, staff shortages and inadequate transportation. "Take Gallipoli," says McEwen. "The men were suffering from dysentery. There were not enough hospital ships to cope with taking the casualties from Gallipoli to Egypt, so they were put on troop transporters." In one instance there were 500 men to one bedpan. In Mesopotamia, where they were bringing the wounded up the Tigris in barges, McEwen says: "The nurses actually had to tie the men's trouser legs round their ankles to stop the faeces pouring out."

Sister Millicent Peterkin, who trained in Edinburgh and worked on barges used to transport the wounded from clearing stations in France, described the conditions on those boats, where the lack of air was problematic - particularly when they were transporting gas-attack victims. "Notwithstanding the fact that they were supposed to be washed all over, and have their gassed uniforms removed in hospital, they still seemed to constantly exude the smell of gas, their breath being especially foul," she said. "Frequently, also, they were badly burned and covered with huge watery blisters. More than once, evacuating such a load, I have felt quite 'gassed' myself, with sore eyes, sickness and difficulty breathing."

On Lemnos island, where Gallipoli casualties were treated, nurses initially slept on rocks. Water was rationed to two pints a day, and this had to cover drinking, washing and laundry - despite the fact that at one point, half the men had dysentery.

McEwen believes that one of the reasons we know so little of this story is that many nurses chose to stay silent. Some wrote to nursing journals to report on the scandalous conditions, but they did so anonymously to avoid being pursued under the Defence of the Realm Act. One unnamed correspondent wrote that in Egypt there were too few nurses and not enough beds for the Gallipoli casualties, and because of inappropriate linen the men got bed sores.

Many of those who did speak out were Scots. "We've always been the underdog," explains McEwen, "and if something's not right we've always had to shout about it. It's the old Scots sense of injustice." Scottish nurses, she says, wrote home and to parish newsletters and nursing journals about what was happening. "They were saying 'whatever you hear, things are worse.'"

But McEwen believes there was a very respectable reason why many nurses didn't talk about their experience. "If you're a nurse, you don't talk about people you look after. That's a very private contract. You are privy to a time in a person's life when they are most vulnerable." The scale of the suffering also played a part. "How do you begin to tell people that it really was as bad as this?" muses McEwen.

Christine Hallett, author of the soon-to-be-published Veiled Warriors: Allied Nurses Of The First World War and an adviser on The Crimson Field, doesn't agree that nurses were silent at the time. Rather, she suggests: "It's that we haven't dug out what they said. Lots of letter and diaries were kept and sent back home and there are many memoirs of the war that have been hidden away."

After the war, it was often difficult for nurses to get war pensions - they were not added into the pension legislation until 1920. Then there was the problem of proving that illness or trauma had resulted from work. "Psychological injury," says Hallett, "tended to be seen rather less as a result of something that had happened than a natural weakness." Some, though, she notes, were diagnosed with hysteria, others with "disordered action of the heart".

The death figures for nurses are, of course, tiny in relation to the 900,000 men who lost their lives in the First World War. The biggest impact of that cruel conflict was undoubtedly upon young men, whose bodies were sent "up the line" repeatedly to be demolished. But women were there, some of them right in the thick of it - and the impact of the war on those who cared for the horrifically injured, has, until recent years, been entirely neglected. Even if they weren't physically affected themselves, many were psychologically altered.

One nurse, Sister Catherine Black, summed this up particularly eloquently, writing after the war: "It is only looking back on those years I wonder how I managed to get though them. I know they changed us. You could not go through the things we went through, see the things we saw, and remain the same. You went into it young and light-hearted. You came out older than any span of years could make you."

That is, if you came out of it at all. Nearly 400 - possibly more - did not.

The Crimson Field starts on BBC 1 tonight at 9pm.