THEY marched with a zest down the Champs D'Elysees, their very presence signalling that surely the worst was past, their minds pleasantly occupied by the expectation that the victory parade rather than the humble foxhole might be their more regular habitat.

But the American soldiers who strode proudly through Paris on August 29, 1944, would be transported from pomp to awful desperate savagery before the year was out.

They had survived the D-Day landings but more than 8000 Americans, including many in the parade, would not survive the year. The war that was predicted by many to be over by Christmas was to erupt once more to catastrophic effect as Adolf Hitler threw everything at the Allied advance through France.

Antony Beevor, measured - even disciplined - in his prose, sums up the purpose of what has become known as the Battle of the Bulge in a quote from a Fuehrer that resounds with a diabolical nihilism: "We may go down but we will take the world with us."

The most immediate, striking impact of Ardennes 1944 is to serve as a remembrance that the Second World War did not end on the beaches of Normandy. Beevor's latest work thus is almost a companion piece to his brilliant Berlin, the chronicle of how the Russians brought about the endgame almost a year after mainland Europe was invaded by the Allies.

Ardennes 1944 also serves as first-rank military history with Beevor, assiduous and resourceful in research, proving a detailed account of how at 5.20am on December 16 the artillery of the Sixth Panzer Army provided the starter gun to a battle that may have raged at its considerable height on to Boxing Day but that had profound implications on how the war ended in Europe in the May of the next year.

The facts are here. There are maps, orders of battle, statistics, casualty lists, dates, times and specifics of ordnance. Beevor's triumph, however, is to add layers to a book that is gently but precisely judgmental, acute on character and gaudy and grisly in detail.

In military terms, Hitler's attempt to push the Allies back into the sea was almost certainly doomed from its inception. Beevor points out that a failure of military intelligence, mistakes by both Field Marshal Bernard Montgomery and Lieutenant General Omar Bradley, and a preponderance of callow troops gave the Germans opportunities that they just failed to exploit. His arguments are strong, supported by excellent sources.

His further layer - the investigation of character and personality - is similarly forensically researched but more dramatic in conclusion. Beevor has a justifiable reputation for scholarliness but this should not be mistaken for dryness of tone or conclusion. Monty, the egomaniac, is suspected of having some form of Aspergers Syndrome, such is his lack of emotional intelligence. Ike Eisenhower, the general entrusted with leading and directing a bunch of egotistical generals that included George Patton, later famously described Monty as a psychopath.

Beevor's verdicts can be similarly brutal though they are always informed by the realisation that those who lead men to inevitable death and occasional glory must be extraordinary. With his sure hand on detail and his strong opinion on how and why the German offensive was prosecuted and why it failed, there is a temptation to suggest that Beevor makes order out of the chaos of war. He does not. He does something more clever, more enlightening and more substantial.

He shows how plans freeze on icy roads, how individual acts of bravery have significant effects, how generals can be wrong but proved right by the vagaries of weather, fortune or a providence that is unfathomable.

He tells of how Patton ordered the chaplain to compose a prayer for good flying weather so that the air force could support his troops. The subsequent clearing of the skies aided the blunting of the German attack and earned the chaplain a commendation. This is just one of the observations that pepper Beevor's account. He adds Ernest Hemingway, JD Salinger and Kurt Vonnegut to the cast of generals, frontline troops and desperate civilians. He uses the reflections of the three writers to enhance some of his own. Thus this is a military history that points out that Marlene Dietrich wore a dress so tight when singing for troops that she did not wear underwear, that Hemingway clogged up the plumbing system of the Ritz in Paris by firing an automatic pistol at the cistern, that a soldier, far from home and near to starvation, could offer $75 to a comrade for a 13-cent can of Campbell soup.

It is the last of these anecdotes that testifies to the profound impact of Beevor's work. He accepts there is a strategy to battle and that there are factors such as manpower, materiel, quality of leadership and of soldiering that must be annotated before anything can be explained or understood. But there is that aspect of war that is beyond comprehension for those who blessedly have no direct experience of it.

Thus Beevor does not look away from the shootings of prisoners by the Germans and the reprisals by the Americans. He includes the gory, the garish. There is one scene where a US soldier has hung a dead German from a tree and has lit a fire beneath him. The purpose is to thaw the corpse, allowing the survivor to prise the boots from his foe. There is another scene, just before the Ardennes conflagration, when US soldiers under fire in a forest died while accepting a meagre Thanksgiving dinner. Their major survived. But every Thanksgiving Day he walks away from an uneaten meal to cry in his backyard.

This is war. It was not over in the Champs Elysees of August 1944. It was never over for many who survived.

Ardennes 1944: Hitler's Last Gamble by Antony Beevor is published by Viking, priced £25