General Roméo Dallaire is a man who’s been to hell — and returned there many times. The Canadian commander of the tiny United Nations force in Rwanda in 1994, he tried desperately to warn his superiors in New York of the approaching genocide but was ignored. Without the manpower or the operational freedom to prevent the catastrophe he was forced to stand by and watch as the horrific ethnic killings, in which 800,000 died, mounted around him.

Cast adrift in Africa and increasingly unstable, his life became a ceaseless struggle through a world of corpses piled high, the gruesome remains of families hacked to death with machetes, often people he knew.

“I still can’t go into grocery shops,” he says heavily. “I can’t face the sight of red meat, of raw flesh. I can’t even face the fruit and vegetables. Their sight and smell carry me straight back to when I had to pick my way through fruit sellers in Kigali, trying to ply their trade amidst the piles of rotting bodies.”

In his bestselling book he talks of seeing what he first took for terrier dogs — rats grown to gargantuan size from gorging on human remains. And for months he still found himself, as the UN man-in-the-middle, in touch with men like Colonel Theoneste Bagosora, the army chief most responsible for the massacres: hence the title of his memoir, Shake Hands with the Devil (Arrow Books).

Dallaire tells frankly how, by the end, his fellow officers were worried by his increasing impatience, his emotional outbursts and other signs that he wasn’t coping. Finally, when the killing had stopped, he was sent back to Canada. His subordinates were convinced that another fortnight in the thick of the Rwandan nightmare would have killed him.

Looking back, he feels he missed many signals from his wife and three children that they, too, were struggling and that Rwanda had disturbed him far more than he was initially willing to recognise. In the end he went through therapy and a lot more, as did two of his children, but the family has stayed united and strong.

“My father and my wife Beth’s father helped liberate Normandy. My son Willem is fourth-generation military. But it’s not just a question of being strong or loyal, it’s a question of understanding when human beings are put through more than they can take.”

After Rwanda everyone wanted Dallaire to tell his story. He procrastinated, scared of the memories, the nightmares. He found a delightful young woman journalist to work with, Sian Cansfield but, it later emerged, Sian had her own problems with depression. These she hid as they went back into hell, into the recollection of those terrible months of 1994, but gradually she grew sad and withdrawn — and then committed suicide.

“There were two things which really tipped me over the edge. One was when I had to go back to my notes from 94. I spread them out and up rose the pungent smells of that period, the worst of which came from our constant burning of dead bodies with diesel oil. It took me three weeks of therapy to get over that. But, of course, the other thing was Sian’s suicide. It was just too much.

“She was such a fine young woman and she, too, seemed to have been killed by Rwanda. Now I realise, of course, that she had many other problems I didn’t know about then.”

Dallaire suffered a complete breakdown. “I drank a lot of whisky and then I took one of those old-fashioned razor blades and slashed my wrists and arms and legs, every vein I could. I remember the warm blood gushing out everywhere and the most incredible feeling of relief and relaxation I have ever felt in my life. It was wonderful.”

His sister-in-law found him in time, rushed for help and he survived. He was given an honourable medical discharge from the Canadian army in 2000.

But then a new battle began, one he is still fighting. “I now know I was suffering from post-traumatic stress disorder (PTSD) and that this is very common among the military. Unfortunately, the army is a very Darwinian organisation. If you can show off a physical battle wound in the officers’ mess, you’ll never have to buy another drink in your life, but the army doesn’t like to know about injuries which happen inside your head. These are seen as dishonourable wounds, like self-inflicted injuries to get out of combat duty.”