BASTOGNE, BELGIUM -- They are old men now, all of them, and their memories after half a century are distilled to essences, to something pure and remote and terrible.

They remember the snow, the cold, the rush of artillery in the early morning darkness. They remember fear, hunger, confusion. They remember the dead, and they want you to remember the dead too: how those who fell assumed a deep claret color because blood in the capillaries beneath the skin froze so quickly.

Fifty years ago this week, the U.S. Army stumbled badly for the only time in its crusade to liberate Europe from Nazi Germany. Among the relentless procession of 50th anniversaries recalling World War II events in Europe, the Battle of the Bulge commemoration is the bitterest. By underestimating the German capacity to counterpunch, in what an official account calls "one of the worst intelligence failures in the history of the U.S. Army," the Americans would pay a horrific price: 81,000 casualties, including more than 19,000 dead. The German attack was so grim that Lt. Gen. George S. Patton Jr., not known for his faint-heartedness, confided to his diary, "We can still lose this war."

The Army bent but did not break; the German onslaught bowed back the Allied line along an 85-mile front, giving the battle its name. Fighting swept across 2,000 square miles of Belgium and Luxembourg. Some villages changed hands four times. In scope, intensity and duration, it was the single greatest battle the Army fought in the war.

And in the end, the Bulge broke the back of German resistance, opening an unremitting assault on Fortress Deutschland. In six weeks of fighting, Germany lost 120,000 soldiers, some 1,600 aircraft and virtually all remaining armored reserves. Four months after the Bulge, Adolf Hitler was dead and the Third Reich had surrendered.

This weekend has been a time for contemplation and commemoration where 50 years ago there was only death and misery. Several hundred American veterans returned to Bastogne on Friday for a memorial service and a parade. "We will be worthy of your sacrifice. We will not forget you," Gen. George A. Joulwan, NATO's supreme commander, told them during a sleet-spattered ceremony on a hill overlooking Bastogne. "You have given Europe 50 Christmases in peace."

And for 50 Christmases the men who came back here this weekend have been thinking about what happened.

Estil Robertson was a 22-year-old company first sergeant in the 501st Paratroop Regiment, 101st Airborne Division: "My company was at a crossroads about three miles north of Bastogne when the Germans attacked. I remember a lot of shell fire. So many young men died, 19, 20 years old, men who hadn't really lived yet. It was cold, miserable -- we were fighting in the snow all the time. The fighting was continuous for nine days."

A German attack through the Ardennes was Hitler's brainstorm, born of desperation and opposed by his senior military commanders, who correctly recognized that the loss of 3.8 million soldiers in five years of fighting had rendered Germany too feeble to sustain a major offensive. But with the Allies on the western front paused to regroup following their sweeping breakout from Normandy in July 1944, Hitler hoped to slice between the British in the north and Americans in the south. If German forces could seize the key port at Antwerp, pinning the British against the North Sea in a second Dunkirk, the western Allies might consider a separate peace.

In a plan code-named Watch on the Rhine and then renamed Autumn Fog, Hitler in September picked the Ardennes for his armored thrust. Offering a direct avenue to Antwerp, the forested hills were close to the dense woods of the German Eifel region, where attackers could assemble undetected.

Although German armies had punched through the Ardennes three times in seven decades -- in 1870, 1914 and 1940 -- American intelligence considered an attack unlikely. The area was used by Gen. Dwight D. Eisenhower as a place for battle-weary units to rehabilitate and for green divisions to ease into combat. Only five divisions were stretched across a 100-mile front.

Further deceiving the Americans was strict German radio silence. Hearing nothing, U.S. eavesdroppers assumed nothing was happening. In fact, the Germans moved three armies with 18 divisions into attack positions with remarkable secrecy. Even the hooves of the horses used to pull wagons and artillery caissons were bound with straw to muffle any telltale clopping.

Garfield Brown, then 20, was a corporal in the artillery at St. Vith. "There were Germans running around in GI uniforms. At checkpoints, trying to figure out who was real and who wasn't, our sentries would ask questions like, 'Who won the World Series?' I didn't know. I had come from the boonies, and we didn't even own a radio."

The offensive opened at 5:30 a.m. on Dec. 16, 1944, with an artillery barrage. Approximately a quarter million attackers flung themselves against 80,000 defenders. German commandos infiltrated behind the lines with checkered results. Most of the paratroops dropped near Belle Croix to disrupt communications were promptly captured. But 33 English-speaking saboteurs, driving captured American vehicles, caused havoc by blowing up fortifications and sowing panic.

"Three times I was ordered to prove my identity," Gen. Omar Bradley later recalled. "The first time by identifying Springfield as the capital of Illinois; the second by locating the guard between the center and the tackle on a line of scrimmage; the third time by naming the then-current spouse of a blonde named Betty Grable."

Atrocities occurred. On Dec. 17, a German SS unit machine-gunned 72 captured American soldiers in the town of Malmedy. A dozen who escaped hid in a cafe; the SS set fire to the building and shot those who emerged. Five days later, U.S. troops shot and killed 21 Germans fleeing a burning house under a Red Cross flag at Chenogne, according to historian Martin Gilbert.

Within 30 hours, troops from the 6th Panzer Army were at St. Vith. The 5th Panzer Army, attacking on a 30-mile front, cut off and captured 9,000 U.S. soldiers from the 106th Infantry Division, a mass surrender second only to Bataan in American history. Sixteen new German jets known as Blitz bombers, flying the first jet aircraft attack mission ever, hit railroad targets in the Ardennes and a ball-bearing factory in Liege on Dec. 24. The spearhead of the attack pushed to within four miles of the Meuse River, 60 miles deep into what had been Allied territory.

Delmar Richards, then a 24-year-old sergeant in charge of a machine-gun squad, had survived Omaha Beach with the 1st Infantry Division. In the Ardennes, he helped reinforce bloody Elsenborn Ridge on the north flank of the battle. "The Germans brought their tanks over the top of our foxholes, and they would wheel around in a circle, caving in the holes with their tracks. I told my men, 'No prisoners.' Our captain said to hold at all costs. We did."

The German commander, Field Marshal Gerd von Rundstedt, recognizing that his forces were overstretched, wanted to withdraw after a week of fighting. Hitler refused. Meanwhile, Eisenhower had met with Patton and Bradley at Verdun on Dec. 19. In disaster lay opportunity, and the supreme commander ordered Patton to make a sharp left turn with his 3rd Army and hit Rundstedt in the flanks from the south.

As Patton wheeled his divisions around, U.S. troops in the Ardennes stiffened. The 99th Division, having been in the line only a month, fought with savage tenacity along Elsenborn Ridge. The 101st Airborne, rushed to Bastogne when the offensive began and wearing white Belgian bedsheets for camouflage, was surrounded in a pocket barely five miles in diameter. Asked to surrender on Dec. 22, the besieged U.S. commander, Brig. Gen. Anthony McAuliffe, famously replied, "Nuts!" Asked to elaborate, the Americans added, "Go to hell."

Still 70 miles from Antwerp, the German tanks began to run out of fuel. On Dec. 23, thick clouds and low-lying fog that had draped the Ardennes for a week finally lifted. Hundreds of American fighters and bombers swarmed over the German formations.

For most of the American soldiers involved in the battle, Christmas was just another day to try to stay alive -- although Patton was particularly proud of delivering turkey dinner to his army. On Dec. 26, his troops managed to punch through to Bastogne, opening a corridor only 300 yards wide but sufficient to keep the town in American hands. Across the immense battlefield, the Germans were slowly driven back to the east, one hill at a time.

Lt. Walter Grabowski, now 72, was a P-47 fighter pilot from Niagara Falls, N.Y. On Dec. 26, he was escorting C-47 cargo planes dropping supplies to Bastogne. "I was Blue 4, Tail End Charlie on the right side. To the back of me, C-47s as far as you could see. It was 9:30, 10 o'clock in the morning, gorgeous, sunny day. Then a German Me-109 and a Focke-Wulf came through our formation, trying to get the C-47s. But we got the Germans first."

The fighting would drag on for weeks before the original battle lines were finally restored. St. Vith was not recaptured until Jan. 23. But the Germans had shot their bolt, leaving little to protect the fatherland. U.S. soldiers, as Patton wrote, "were chasing a sinking fox and babbling for the kill." A new American offensive was launched Jan. 29, one that would carry the liberators across Germany and into Czechoslovakia.

Pfc. Steve Bull Bear was a 21-year-old rifleman in the 8th Infantry Division. Pelted with freezing rain in Bastogne on Friday, it all came back to him. "Cold, terrible, sleeping in foxholes. Hungry. Lonesome. And having a fight."