It must be even less so if you are in a distant, dangerous, inhospitable place where your comrades die daily and where it is ­difficult to tell friend from foe. That is the situation 9000 British soldiers find themselves in today in Afghanistan.

This year alone more than 100 soldiers have died there. That this is an unpopular war need not be underlined. Take any poll and the outcome is the same, a message to the Government to pull the troops out. But even as we deplore the war we must add that we fully support the troops. They are not in Afghanistan because they want to be but because it is their job and their duty.

As New Year approaches, however, many must curse their choice of profession, their thoughts turning to home, their loved ones and the traditional celebrations. Their fate, though, has been mirrored by soldiers down the centuries, be they Roman legions huddled under Hadrian’s Wall or the generation of lost poets, such as Rupert Brooke, who, while railing at the imbecility of war, dreamed of their homes with a passion only those fearful of never seeing them again can articulate.

“God I will pack and take a train,/ And get me to England again,” wrote Brooke in 1915 in the Dardenelles. He never did see England again. That is the reality of war, which we all hope will one day be over, as was hoped after the First World War – the war that was meant to end all wars.

More recently, in 1998, military historian John Keegan concluded that “the worst of war is now behind us”. Henceforth, he said, “mankind, with vigilance and resolution, will ... be able to conduct the affairs of the world in a way that allows war a diminishing part”. Keegan, of course, was writing at the fag-end of a century in which two global, industrial wars had threatened our very existence. Since 1945, Britain had enjoyed what Keegan called “a blessed half-century”.

Our only unilateral war was the Falklands which, though traumatic for many who participated in it, was minor in the grand scheme of things. As for the Korean and Gulf wars, our participation, noted Keegan, was both legal and laudable. “We have made no serious enemies,” he wrote, “and kept many friends, while responsibly discharging onerous military duties, sanctioned by the United Nations, in scores of trouble spots around the globe. The ordinary British citizen has good reasons for concluding that conflict in our time has been brought under control through wise diplomacy and the deployment of judiciously calculated force.”

Keegan’s optimism was borne of an era which engendered such sentiments. It began, as Iain Banks described in his latest novel Transition, on November 9, 1989 with the fall of the Berlin Wall and ended on September 11, 2001 with the fall of the twin towers of the World Trade Centre. Since then there has been another significant fall, that of the markets, which happened on September 15, 2008.

After more than a decade of relative peace and prosperity, therefore, the world has been thrown into turmoil and carnage. With a gung-ho president in the White House and a compliant prime minister in Downing Street, Britain found itself engaged in conflicts for which even Lord Kitchener at his most bellicose would have had difficulty rousing popular support.

War is very much at the forefront of our thoughts, as the remains of soldiers are flown back from Afghanistan and the suicide bombers continue to wreak havoc in Iraq. What was once a clear-cut goal – the rooting out of those behind 9/11, including the ever-elusive Osama Bin Laden, and the protection of Britain and the United States from future attack by the elimination of weapons of mass destruction – has become so vague that most British ­citizens have difficulty in articulating it.

This is not a situation any promoter of war likes to be in. No-one in their right mind believes in war but some wars are deemed justifiable because the alternative is unconscionable. Angus Calder’s book The People’s War offers some sense of the cohesiveness of opinion that prevailed throughout a nation which for much of the early 1940s seemed to be heading for defeat and into the hands of the Nazis.

Such a war affected everyone, not just those in the firing line but family and friends, politicians and strategists, pacifists and aggressors. Like murder, war is pervasive in its influence. It seeps into hearts and minds. It governs thoughts and sleeplessness, ­provoking fear and foreboding. As it goes on, it enervates, making us question the point of existence.

We may not be immediately endangered but it gnaws at our bones, saturates our confidence, tries our conscience, tests our resolve. Even those who have lived our lives relatively war-free are beset by it, counting our luck, wondering why we have lived without ever being shelled or bombed or bayoneted or tortured when so many innocent others have had their lives violently curtailed.

How to know what it was like to be them? To know, as did airmen in the Second World War, or infantrymen in the trenches in the First, that the odds on their survival were so poor no bookmaker would take the bet? The anger of war poets, especially Siegfried Sassoon and Wilfred Owen, was directed at civilians whom, they insisted, simply didn’t understand what they were experiencing.

Another soldier-poet, Edward Thomas, tried to convey the grimness of trench warfare in his diary, which he kept from New Year’s Day to April 8, 1917 when, a few hours after writing his last entry, he was killed at Arras, one of 150,000 British soldiers to die in six apocalyptic days.

What it was like to receive news of a soldier’s death is described by Vera Brittain, author of Testament Of Youth, on this page. As was the norm in the First World War, she received a standard telegram informing her that her fiance, Roland, was dead. Three years after Roland’s death she learned that her brother Edward had been killed.

Driven by grief, she vented her spleen on Edward’s commanding officer who, infuriated, informed her that when her brother died he was under investigation over allegations that he was homosexual. Given the shame Edward would have suffered if that had been made public, the officer told Brittain that he may have taken his own life or deliberately courted death.

Many things are common to all wars. Here, for instance, is Albigence Waldo, a combatant in the 18th century American Revolutionary War, detailing the lack of resources. Meanwhile, Zlata Filipoci, a Bosnian refugee of mixed ethnic heritage, observes the effect of war on her parents. In Vietnam, David Parks, a black GI, shows that the gulf in understanding between the local population and foreign troops is nothing new. In Britain, in the Second World War, housewife Nella Last sees soldiers far from home whose young faces are engrained with deep lines. There is hope from a POW that the war will end and he will be released and hope, too, from Lord Alanbrooke, one of Winston Churchill’s top aides, that the worst is over and that the war can be won, though who knows when.

Nothing, however, can compare with the graphic letter from Rifleman Burton F Eccles, which manages to be simultaneously jaunty and awe-struck as he offers his family an eyewitness account of Passchendaele, in whose environs a quarter of a million British soldiers lost their lives. “The best of wishes for 1918. May next Christmas be quieter for me,” signs off Eccles. And, in the absence of information to the contrary, we must assume it was.