In this age of cheap patriotism, when the greatest war sacrifice most of us makes is the damage caused to our clothing through pinning on little flags, it's good to be reminded this Memorial Day that it wasn't always so. To the general population of the United States the much-vaunted War on Terror is not dissimilar to the War on Crime, or the War on Drugs – it's a struggle that is fought on our behalf by a group of professionals that constitute a relatively small percentage of our nation. The kind of universal sacrifice that was required during the Second World War, and to a lesser extent during Vietnam, just isn't part of our consciousness. A new book to be published by Steidl later this year may serve as a mnemonic to those who have forgotten.

It contains the work of a young French-American photographer called Jonathan Alpeyrie, a 29-year-old who was born many years after the conflict whose survivors he has spent years and several thousands of dollars documenting. The Second World War had always fascinated him, and in December 2003 he began photographing the veterans who fought in it. His aim was to photograph and interview this dying generation of combatants, something that had certainly been done many times before, but what Alpeyrie wanted to do that was different was to photograph veterans from every country that fought in the war. This is much more ambitious than it sounds. A total of 56 nationalities took part in the conflict, 17 on the axis side and 39 with the allies.

To date he has photographed men from 30 countries, 21 who fought for the allies, and 9 who were with the axis forces. One thing he had going for him was that he lives in New York, a city of immigrants, where the soldiers of many nations settled upon demobilization, rather than face the wreckage that was their homeland. He discovered a third of the nationalities involved there, and another third in Paris. For the rest he has had to travel, hence the price tag of between $30,000 - $35,000 in expenses, most of which he will never recoup. Another hurdle was finding men that had fought with the axis forces who would allow him to photograph and interview them. They were difficult to contact and convince, especially those who volunteered for the Wermacht from countries occupied by the Germans. It is a measure of his determination that he found and photographed such volunteers from Norway, Belgium, Sweden, France and Croatia, although he was careful to make sure that their role was that of fighters, and not other functions such as guards at concentration camps.

It was the similarities of these men-at-arms from many nations rather than their differences that interested him – the shared courage, fear, and pride, in short the camaraderie of men who have participated in an experience that is so idiosyncratic only those who have known it can understand it. To look at the portraits he has produced for the project it is difficult to see the warriors that they once were. Age and the afflictions that accompany it are now something else they all share. The frail, thin bodies are too small for the uniforms that once fit snugly. The rows of medals, especially of those who served with the Soviet forces, seem too heavy for them to bear on their bird-like chests. And yet, on occasion, we get glimpses of the young men they once were. The wonderfully named Thomas Louis Gilzean, a doughty Scot with a stern countenance, has obviously remained a man not easily pushed around even after his military service; Fernand Kaisergruber retains the cold intensity in his clear blue eyes that they probably always had; Alfons Ukkonen displays the same dogged determination in the set of his jaw that caused him to join the German army to defend his Finnish homeland against the Russians; Mrav Hakobyan, lined and grizzled, still has some of the aspect of a Cossack warrior.

These are in the minority. Most of the men that inhabit the pages of this book look like the lawyers, accountants and clerks that they became after their fighting was done. For the majority, although not all, soldiering was not a career but an urgent necessity, and for many the defining experience of their lives. Almost certainly within their number are those who did acts that we, as civilized people, would condemn, but war itself is uncivilized to the extreme, and we should not be shocked by the uncivilized behavior of those we call upon to participate in it. As the photographer himself says, "It is difficult to judge and criticize many decades after it happened. We as individuals do not know how we would have behaved under the same circumstances. Their choices 60 years ago are almost irrelevant now."

Why would a young man spend so much time and money memorializing old men whose glory days were long ago? One sentence from a recent interview with Alpeyrie sums it up: "If we had the mentality we have today in 1939 we'd all be German." He believes that understanding their sacrifice puts into perspective the actions that we take now. Although he lost two friends in the attacks on the World Trade Center he says, "I don't think that 9/11 was all that bad. Geographically it only affected a few blocks; the people who died did so in a short period of time. Life moved on. It is strong symbolically, because it was only a beginning. Things will get a lot worse. I am a pessimist about this."

It is the contrast between the sacrifices these old men made six plus decades ago and the lack of commitment he sees today that Alpeyrie wants to highlight. "Iraq doesn't touch the nation. It touches the nation when you lose 400,000 in four years, or in Ypres, when the British lost 20,000 on the first day of battle." If war is brutal, then his assessment of how we should view it is equally brutal: "If you're not willing to accept the casualties you should not be waging war. You should stay at home."

As the war in Iraq drags meaninglessly on, as the Taliban resurge in Afghanistan and Osama Bin Laden remains at large in the mountains between them and Pakistan it is a judgment that all of us, liberal and conservative, red state and blue state, pro-war and anti-war, should remember this Memorial Day.