Max Hastings: To today's soldier, war is every bit as bad as the Somme

In Amara, Iraq, in 2005, a 32-year-old Welsh lance corporal was shocked one night after a firefight to be shown a shard of shrapnel protruding from his own body armour. Back home, his girlfriend was pregnant with their first child. His behaviour changed immediately. He had to have meals brought to him. He refused to take his helmet and body armour off ever, even in bed. He was swiftly evacuated as a medical casualty, and a good and valued soldier signed himself out of the Army.

One of the curiosities of war, and our attitudes to it, is that in each conflict norms of experience, and perhaps also of soldiers' tolerance of it, prove to be different. Objectively, it might be said that the action which caused that Welsh lance corporal to feel that he could not go on was a very modest affair by comparison with what was endured year after year by those who served in two world wars. During a conversation about the Falklands war, the former prime minister Harold Macmillan said slowly: "In my war, a battalion which cost only 17 killed wouldn't think that it had been in a battle." That was because the norm that prevailed between 1914 and 1918 was utterly different from that of 1982 or, indeed, from that of 2005 or 2007.

No soldier of a modern democracy who has participated in any of the wars of our own times can exactly equate these contemporary experiences with that of the men who fought in the First or Second World Wars. In wars today, soldiers experience the shock of battle for hours, sometimes repeated at intervals over weeks or, at most, months. It is hard, if not impossible, for our imaginations to grasp what it must have been like, for those who took part in battles like the Somme or Stalingrad, who suffered for months and even years on end constant fear and hardship, together with losses on a scale no modern Western army has known.

Objectively, we can say that the lot of a modern soldier, even one committed to war, is enviable compared with that of our grandparents' generations. Yet that does not mean that, for the man at the sharp end, the predicament of battle is subjectively less awful.

I always used to be impatient of the widespread American conviction that Vietnam was a uniquely awful experience for the combat soldier. Yet looking back across 35 years we can today see why, subjectively, American soldiers found Vietnam so awful an experience. First, from the mid-1960s onwards, they were fighting a war in which confidence in their own strategy, leadership, tactics, equipment and training was sorely lacking. Second, there are few experiences more dispiriting to any army than to fight among civilians and to see at close quarters the terrible sufferings of innocent women and children. But their greatest source of misery and demoralisation was the knowledge that their struggle did not command the support of the public back at home. Nothing is more dispiriting for soldiers risking their lives than to be denied a belief that their own nation and people think what they are doing is worthwhile. This, surely, must be the case for our soldiers in Iraq today.

The principal prop, the vital support of the armies of the two world wars – including the German and Japanese – was the belief that they were fighting for their own peoples, their own families, their own homes. Their experience was shared and understood by their entire societies. This is not to say that what soldiers went through on the Somme or Stalingrad was acceptable: only that it kept alive in men under the most extreme conditions of horror and fear that flickering candle of faith that they might be suffering and dying for a purpose.

A decade after the Falklands war ended I went for a drink with a young marine officer who lost a foot on a mine almost on the last day of fighting. For me, by 1992, the conflict, which I had witnessed as a mere journalist, was long over. We cherished only warm and often sentimental memories. Yet it was clear that his entire life had been blighted by what had happened. He had been forced to abandon his military career. He had obviously suffered great difficulty in adjusting his life. Above all, he had found it hard to live through the decade after his disablement in a civilian society with no real understanding of what he had been through and among civilian contemporaries without much sympathy for his experience.

For the modern warrior, the strain of days or weeks of tranquillity can be very great if, at every moment, a soldier knows that the harmony of nature may be pierced by bomb, sniper's bullet or booby trap. To the layperson, the experience of fighting terrorism – confronting an enemy who possesses only small arms – might seem less awful than enduring combat against a foe with rockets, artillery and air power. But I do not think this always seems so to those at the sharp end.

What preserves our sanity and mental balance in normal civilian life is trust. We sit in our gardens or offices assuming that an aeroplane will not crash on to our lawns. That is normality. The consequence of terrorism, and even more of high-intensity battle, is to shatter that basic human fabric of trust in our daily environment. In a combat zone, soldiers must live every moment in the knowledge that death may be stalking them – and that knowledge erodes everyone's resources of emotional strength and poise, albeit at different speeds. As Lord Moran, Winston Churchill's doctor, memorably wrote, courage is capital, not income – a quality of which all men have variable but expendable amounts. Some endure longer than others, but all can endure only just so much.

It is irrelevant to a soldier who experiences the misery of traumatic stress that others in history have faced much worse at Passchendaele or Normandy. Norms change. The shock of finding oneself in mortal peril, of seeing others around one blown to fragments or hideously maimed, can be as great in a single day of battle as in a year. The only common denominator is that no decent soldier has ever despised those who succumb to trauma on the battlefield or afterwards. They are almost unfailingly the object of a comrade's compassion – as they should always be of ours.

Sir Max Hastings's fee for this article has been donated to Combat Stress, the Ex-Services Mental Welfare Society

Further browsing: Visit combatstress.org.uk for information on how, for more than 80 years, the charity has been helping service personnel with psychological disabilities