Injuries caused by operational stress and trauma have always been a part of warfare. These are the wounds not caused "by a direct enemy projectile or explosive," as one textbook says, but those that injure the mind or the spirit. These wounds too can be fatal.

Doctors with fighting units have been describing what we'd call the psychological effects of soldiering ever since the dawn of modern medicine in Europe. The first medical paper on the subject was published in 1678. Its author observed anxiety, depression, disturbed sleep and insomnia severe enough to lead, when not dealt with, to madness or mysterious death. It was only the vast scale of the First World War, however, which forced medical establishments to confront the treatment and rehabilitation of operational stress injuries. Doctors have been engaged with the issues ever since.

The symptoms and the injuries themselves vary according to the nature of the warfare and, equally important, the reception given to the injured soldier. Intense combat can produce severe psychiatric symptoms. Intermittent stress can lead to substance abuse, depression, anxiety and amnesia. A constant low level of operational stress - especially in the context of futility or defeat - can lead to evacuation for sheer fatigue or an obvious physical illness such as muscular tremor, vomiting or diarrhea. And single traumatic events - including events far away from combat - can generate vivid, ever more frequent nightmares.

Efforts to predict which combatants might be more vulnerable have broadly failed. This has led some medical research away from individual psychiatry and toward questions of social behaviour. Is there, for example, a stigma so strong that a soldier is unwilling to admit, even to himself, that he's injured? Does the world regard him as a legitimate casualty, or as merely a weak individual? And is this soldier returning to a place that accepts him gratefully as a veteran, or will he be scorned as promoting an unjustified war? Injuries sustained sometimes get buried deeply within, where they can fester and poison other parts of the veteran's life to the point of total breakdown.

Many of these factors were present in operations overseas during the 1990s. The violence was very personal, for these were not high-tech wars, and Canadian military personnel were exposed to unimagined evil. Yet the actual combatants were often ambiguous and the use of force was limited; sometimes Canadian soldiers were forbidden from preventing ethnic cleansing even when they had the combat power to stop it. Less than 24 hours after this kind of experience, they could once more be home - a stunning transition - where they would discover that most Canadians knew nothing about what they'd been doing. As the symptoms of unresolved trauma and stress began to emerge, wounded veterans also found that most medical and pension arrangements did not account for their kind of injury. Many veterans received little or no treatment and so their frustration grew as their injuries remained suppressed within.