It started with a vicious ripple of cannon at 5.30am on a wintry morning. No inch of the 80-mile Allied front was spared. The date was December 16, 1944 and the mighty Nazi army was embarking on its last bid to win the war for Hitler.

In blinding snow, German infantry and tanks filed into the forests of the Ardennes region of Belgium and Luxembourg. They had waited until weather conditions were at their worst. Most American defenders never knew what hit them.

Due to its challenging terrain of twisting valleys, high wooded peaks, numerous rivers and poor road network, the region was long considered a quiet sector, where veteran units could rest and those with limited combat experience were introduced to war. The arrival of accurate shell-fire, panzers and German troops threw those on the receiving end into chaos and confusion during the initial days.

The Germans dubbed their surprise attack Operation Wacht Am Rhein (“Watch on the Rhine”), changed in the final days for security reasons to Herbstnebel (“Autumn Mist”), and aimed to break through American lines, push them away from the German border – capturing fuel stocks as they went, to compensate for their own deficiencies, and retake the port of Antwerp to halt the flow of supplies to the Allies.

As the resulting panzer corridor would slice through Allied positions, separating the British and Canadians in the north from French and US Forces further south, Hitler also hoped for a strategic split in the coalition ranged against him, as the Allies bickered as to where the blame lay for the German incursion.

The Wehrmacht achieved complete surprise due to their tight security arrangements and a failure by the Allied codebreakers at Bletchley Park to foresee the attack.

The onslaught came as a rude shock to the Americans, whose lines in most sectors were overrun, resulting in heavy losses – including many taken captive, such as the future novelist Kurt Vonnegut. In the first few days, several German units murdered American prisoners, notably at Malmedy on December 17, and several cases of battlefield atrocities against Belgian civilians also took place.

Allied commander Ike Eisenhower’s two strategic reserve formations, the 82nd and 101st Airborne Divisions, just beginning a much-needed rest from frontline duties, were rushed to reinforce the town of Bastogne and further north, as dramatically portrayed in the hit Steven Spielberg-Tom Hanks 2001 TV drama Band of Brothers, starring Damien Lewis.

At a crisis meeting held in Verdun on December 19, Eisenhower directed that his friend, Omar Bradley, headquartered in Luxembourg, should command George S Patton’s Third US Army and other beleaguered forces in the southern sector of the German penetration, soon to become known as “the Bulge”. Those troops further north, including the US First Army, would be temporarily led by the Allies’ other army group.

Eisenhower’s order brought the British firmly into the Ardennes campaign, for the northern-flanking higher headquarters was the 21st Army Group, based in the Flemish Belgian town of Zonhoven and commanded by Field Marshal Bernard Montgomery.

Monty could see that while the American First and Third armies could contain the two flanks of the German bulge, a backstop was needed to prevent the Nazi blitzkrieg from breaking out westwards beyond the River Meuse. Accordingly, he ordered a British corps, led by his old staff college student Brian Horrocks, to garrison the riverbank and take part in squeezing the northern shoulder of the Ardennes pocket.

The British 6th Airborne, 51st Highland and 53rd Welsh Divisions, plus 29th and 33rd Armoured and 34th Army Tank Brigades were immediately alerted for duty.

Most had hunkered down for Christmas but off they went and soon encountered their opponents. Towards midnight on December 23, a Jeep manned by three Americans failed to stop at a joint Anglo-US checkpoint at Dinant on the east bank of the Meuse.

When the vehicle careered through a natural rock opening in the road by a prearranged signal, a few hundred yards further on, Sergeant Baldwin of the 8th Rifle Brigade (a British infantry battalion) pulled a necklace of anti-tank mines across the road, blowing up the Jeep and killing its occupants.

All three were found to be wearing US helmets and greatcoats over German uniforms. In their pockets were detailed plans of the Allied defences. It was a reminder that English-speaking SS commandos were on the loose behind Allied lines, riding captured US vehicles.

During the following day, armour of the Royal Tank Regiment duelled cautiously with the 2nd Panzer Division, whilst British and American rocket-firing Typhoons, P-47s and P-51s hit their supporting units.

The poor weather that had cloaked the first few days of the German attack had lifted and allowed Allied air observers to direct British 25-pounder ground artillery on to targets with great accuracy. They noted how conveniently the dark enemy vehicles showed up against the snowy background. According to records, it was obvious that the panzers were short of fuel, as each German tank was observed to be towing up to three trucks.

These skirmishes represented the furthest west the Germans penetrated in the Ardennes during the offensive. Meanwhile, from the south, thundered General George S Patton’s Third Army, whose vanguard first reached the besieged town of Bastogne on December 26.

Four days earlier, when given an ultimatum from the German forces outside demanding “the honorable surrender” of the town within two hours, its embattled commander, Brigadier General Anthony McAuliffe, sent a brief and succinct reply that has now entered the history books: “To the German Commander: NUTS!”

Having made their position clear, the Americans dug in and waited for the attack, the 101st holding out until Paton’s reinforcements arrived.

On December 16 this year, US Army veterans joined with members of the 101st Airborne for a parade in Bastogne marking the 80th anniversary of the Battle of the Bulge. Following the commemoration, as is common, veterans joined officials and the royal families of Belgium and Luxembourg in throwing walnuts to crowds from a snowy balcony at the town hall. The annual celebration recalls Brig Gen McAuliffe’s reply: NUTS!

Following the liberation of Bastogne, the Battle of the Bulge continued for several more weeks and the front was still chaotic when two British officers drove through fog, ice and snow to set up their headquarters in a hotel on New Year’s Eve. They were met, much to their astonishment, “by a receptionist and a head waiter in a tailcoat”.

On enquiring how long ago the Germans had left, they were amazed to be told “the Nazis had departed through the garden 10 minutes previously”.

The weather was such that when Wing Commander Desmond Scott, in charge of a wing of Typhoon fighter-bombers, was driving his Jeep through the region, he noted “we kept running into masses of super-cooled fog. As soon we hit this, the windscreen became an ice shield and we drove with our heads out of the side of the Jeep, several times sliding off, and had to be pulled out each time by passing trucks.”

Film star David Niven, then a lieutenant colonel in a special signals unit who was driven by fellow actor, Private Peter Ustinov, recalled suspicious American GIs stopping their vehicle at checkpoints because of their British accents.

Niven rarely knew the right password, but responded with clueless charm. He would say: “Simply haven’t the foggiest idea but I recall I made a picture with Ginger Rogers in 1939 called Bachelor Mother.”

The star was ushered through with an “On your way, Dave, and good luck!”

Another movie icon, the Berlin-born Marlene Dietrich, was putting on a two-hour Christmas show for frontline GIs and had to be spirited away at high speed, for her country of birth had put a price on her head.

The initial shock of the German attack had worn off within three days and a general counterattack by all Allied forces began just after the New Year.

By January 11, a link-up was made between British troops and GIs, when the Scottish Black Watch encountered the US 635th Destroyer Battalion in the snow-laden town of La Roche. One of the Scotsmen, Hamish McAllister, recalled: “We crossed over the wrecked river bridge and met American soldiers in their armoured car. We sat down, around a fire of petrol and sand in a bucket, and shared coffee with them.”

Each could barely understand the others’ broad accents. McAllister continued: “Then a photographer with a reporter arrived in a Jeep and we were made to rush down a street from opposite ends, meet and shake hands in the middle.” The posed photograph made headline news around the world and emphasised that the Allied assault was working – and the German offensive was waning.

By January 8, the German High Command ordered a retreat back to Germany, though fighting continued against their rearguard. By then, British and Canadian casualties totalled around 1,400 killed, wounded and missing.

American and German losses would eventually approach 80,000 infantry and 800 tanks – for each side. Churchill later paid tribute to the US Army in the Ardennes offensive. He labelled it “undoubtedly the greatest battle of the war, which will, I believe, be regarded as an ever-famous American victory.

“United States troops have done almost all of the fighting and have suffered almost all the losses. The Americans have engaged 30 or 40 men for every one we have engaged, and they have lost 60 to 80 men for every one of ours.”

To this day, bullet-scarred houses remain in every town, while shallow foxholes litter the woods. Though a predominantly American campaign, the British arrived and fought in conditions of secrecy – and departed with equal stealth.

At the western extent of the German penetration, at Hotton in Belgium, they left behind only a lonely Commonwealth War Cemetery. Most of the 666 interred there are from January 1945.

The dead include 18-year-old troopers of the 61st Reconnaissance Regiment, Daily Telegraph war correspondent Peter Henry Lawless, Ronald Cartland MP, who was brother of the novelist Barbara, and Brigadier Brian Sugden, the 54-year-old commander of 158th Brigade.

They underline Britain’s unspoken and almost unknown contribution to the last great battle in Europe of the Second World War – the Battle of the Bulge.

• Peter Caddick-Adams is the author of Snow and Steel: Battle of the Bulge 1944-45 (Arrow, £16.99)