World War I was meant to be the “war to end all war.” Instead, it caused a boom in industrial military technology, which increased exponentially the destructiveness of war. Only now, nearly a century later, has precision technology (mainly American) reversed the process: The entire invasion of Iraq, for instance, inflicted fewer casualties on both sides than the first day of the Battle of the Somme in 1916, in which the British alone lost 52,000 men. Today, as a rule, the less high-tech a conflict is, the more people, soldiers, and civilians get killed.

But the Great War, as it was known at the time, also led to a boom of a different kind: what Jay Winter calls the “memory boom.” More precisely, he argues that there have been two memory booms in the last century. The first began in the 1890s, when thinkers such as Sigmund Freud or Henri Bergson began studying memory, but was propelled into public consciousness by the war, which created an insatiable demand for memorials and rituals of remembrance. The second memory boom was triggered by World War II, but only reached fruition in the 1970s and ’80s in the commemoration of what had by then become known as the Holocaust, and in the attempts of occupiers and occupied to revise self-deceiving myths about what had really happened in wartime.

Both memory booms figure largely in these two very different books. Neil Hanson’s “Unknown Soldiers” (Alfred A. Knopf, 496 pages, $28.95) is a straightforward account by a British journalist of the fates of 3 million soldiers on the Western Front whose bodies were never identified. Mr. Hanson focuses on three of them – a German, a Briton, and an American – and, using letters and other documents, reconstructs these ordinarily extraordinary biographies. He shows us not only just how these young lives were abbreviated in the abyss of trench warfare, but how their “people” – which, in the idiom of the time, meant family as well as nation – came to terms with their loss.

The most fascinating part of the book, in fact, is this posthumous one. The nationalization of mourning took different forms in different countries, but all had a common focus: the unknown soldier. Mr. Hanson evokes the unparalleled solemnity of the first Armistice Day in 1920, culminating in the two minutes’ silence that fell at the 11th minute of the 11th hour on November 11, and explains why it mattered so much to the bereaved that their grieving should take this particular ceremonial form.

Some criticized the Cenotaph in London’s Whitehall, designed by Edwin Lutyens, as “pagan,” but the war had altered attitudes toward the dead, who belonged to all faiths and none. The unknown warriors were a democratic phenomenon, too – unsettlingly so for some. King George V was none too happy about awarding the Victoria Cross to the American unknown in return for the Congressional Medal of Honor, which he wrongly supposed to be a much more recent and lesser award. Many wanted only to put the carnage behind them – to “move on,” as we say. Yet the urge to preserve the memory of the missing generation proved stronger.

“Unknown Soldiers” resembles its subject: Its strength is its simplicity. “Remembering War” (Yale University Press, 352 pages, $35), by contrast, is a work of great complexity and sophistication. Mr.Winter ranges from war memorials to war films, photography and museums, letters and literature. The common denominator is the theater of memory. There, in the mind’s eye, the traumatic experience of the trenches was transfigured by men and women for whom the fellowship of survival alone gave their lives meaning.

Mr. Winter is well aware that the memory boom, now as then, has dimensions that transcend the domain of the historian. He considers various objections to the cultivation of memory through the interpretation of artifacts or the testimony of witnesses, including claims that this cult of memory is a form of re-enchantment – a substitute for the facts, and a poor one at that. But in a disenchanted, secularized world, it is inevitable that human beings will invest collective memory – and especially the most traumatic memories – with a sacramental or transcendental significance.

What matters most is that our collective memories are not appropriated and manipulated by the unscrupulous. Lest we forget, Hitler’s “Mein Kampf” and Siegfried Sassoon’s “Memoirs of an Infantry Officer” belong to the same literary genre. Charles Maier, Pierre Nora, and Kerwin Klein have all warned that the politics of memory slips readily the idiom of ethnic identity, as in the Serbia of Slobodan Milosevic, for example.

But Mr. Winter believes that there is no escape from the challenge of reconstructing the past, not only for scholars but for the ordinary citizen, with honesty and humanity. He has helped to create the Museum of the Great War at Peronne on the Somme in France. To adapt Nietzsche’s phrase, the use of history in life can always degenerate into its abuse. Modes of commemoration can, indeed must, vary.The Holocaust memorials in Washington, Israel, and Berlin differ as they do because each serves an entirely different though equally legitimate purpose.

Mr. Winter’s book is a plea for academics to get their hands dirty while helping to “prevent people in power from lying about the past.” This injunction should, however, apply not only to politicians, but also to academics themselves: They too exercise power, especially over the young.

On many a campus today, you will hear it said that the commemoration of heroism in war is just imperialist ideology, that the memory of the Holocaust is exploited by Zionists, that our patriotism is nothing but false consciousness. Scholars safe in their tenured chairs think nothing of accusing elected leaders such as President Bush or Prime Minister Blair of lying or acting on the most cynical of motives. Others pretend that American foreign policy is controlled by an occult force they call the “Israel lobby.”

In a free society, politicians do not get away with lies about the past, but what happens in the lecture theater usually escapes such scrutiny. That must change.Academics who dabble in the politics of memory should expect to be held to the same standards as the public figures they criticize.

Mr. Johnson last wrote for these pages about intellectuals in Britain.