The first day of the Battle of the Somme was the costliest in British military history. Here, in abridged extracts from Jolyon Fenwick's book Zero Hour, he explains why we shall always remember July 1, 1916.

We have never tired of revisiting the First World War. A hundred years on, its tragic ironies continue to cast their spell. Names like Gallipoli, Arras and Passchendaele remain bywords for thwarted youth and needless slaughter. There is one battle, however, whose name has come to symbolise a generation’s sacrifice like no other—its doom-laden resonance is almost embedded in our genes: the Somme.

To us, the Somme is synonymous only with bloody failure, but, at the time, after two years of stalemate, the battle promised to be the turning point of the war. Civilians and Government had allowed their generals the failed offensive experiments of 1915. This time, however, on the rolling fields of Picardy, Gen Sir Douglas Haig, Commander of the British Army in France, would put Teutonic barbarism to the sword once and for all.

The belief in certain victory was under- pinned by the introduction to the field of a new kind of army—an army who were all friends. These were the men from the same villages, factories, cricket teams and public schools —the ‘grinning archaic faces’ who had waited patiently outside their local recruiting offices to enlist in August 1914. For the people at home, these civilian ‘Pals’ units would naturally outclass the servile martial professionalism of the enemy. And the civilian soldiers—right up until the final seconds— believed it, too.

The plan was familiar in format, but novel in scale. The British would attack with 13 divisions along a 15-mile front (the Germans having received over 1,500,000 shells) and force a break in the enemy line that the cavalry would then exploit. The objective was the town of Bapaume, 10 miles up the old Roman road from the British lines. It was forecast they would get there in three days.

But the breakthrough never came. On November 18, 140 days after the initial attack, Haig called a halt just short of the ancient burial ground of the Butte de Warlencourt. The remnants of Gen Rawlinson’s 4th Army were still four miles short of Bapaume, having suffered 420,000 casualties. The passage of the fighting was charted by the unrecovered bodies and makeshift graves of 131,000 British and Empire soldiers.

Each phase of the campaign had been costly. But the names of such killing grounds as Delville Wood, Pozieres and Guillemont would not headline the battle for posterity. The ownership of the Somme in popular memory would forever rest with the battle’s first day.

In the early hours of that summer Saturday, a society of miners, stevedores, tramwaymen, errand boys, shipping clerks, railway porters, artists and aristocrats— along with regular and territorial soldiers —assembled in the dirty white chalk of the British front line. At 7.30am (zero hour), the early mist had gone and, against a sky ‘of the kind commonly described as heavenly’, 60,000 men, each carrying at least 60lbs of equipment, climbed out of their trenches and—in the vast majority of cases—walked towards the enemy.

The advancing troops had been assured the German defences would be obliterated by the six-day British bombardment. ‘You will be able to go over with a walking stick; you will not need rifles,’ one general told them. ‘You will find nothing other than the caretaker and his dog,’ promised another. They were wrong.

Sheltered (although, in many cases, tormented to madness) during the unprecedented preliminary shelling in underground bunkers (in places 40ft deep), the majority of the defenders survived. Within two minutes of the British barrage lifting, German machine gunners had scaled their ladders and set up their weapons, unloading belt after belt into the ‘perfectly dressed’ British lines at a rate per gun of 500 rounds a minute. The German artillery also laid down its own carefully ranged stripes of shellfire in No Man’s Land. The explosions looked like ‘a thick belt of poplar trees’.

The resulting carnage appalled even the Germans. In the first hour, more than 20,000 of the attacking troops were killed or wounded. By nightfall, out of a total of 116,000 British and Empire soldiers committed to the battle over the course of the day, 57,470 had become casualties—19,240 of them were dead.

For days following the battle, the British people remained ignorant of the fate of their young men. High-flown headlines of ‘heroic advances’ and ‘enemy trenches occupied’ persisted in national newspapers through the first week of July. But, as early as the Sunday evening, rumours of the disaster were crossing the Channel with the wounded.

As local anxieties grew nationwide, civic dignitaries petitioned the War Office for reports of their battalions. Women besieged town halls and the offices of regional newspapers begging for news. But it would be weeks and months before the machinery of state was able to officially confer on its people—household by household—the true scale of the losses. The country was dumbstruck. Some postmen resigned.

It was not just the numbers. It was who the numbers were: the valiant servants of Empire who, in the hour of need, had selflessly downed their tools and ledgers and together marched off to war. Within a matter of hours, it seemed this noble army had gone. Its wounded survivors, too numerous to hide from the public gaze, were limbless, sightless, senseless or missing half their face. The bereaved held to a Pre-Raphaelite image of their beloved’s death: peaceful, immutable, intact under a cross of blinding white. But it was a vision they found hard to keep to. From July 1 alone, there was not enough left of 6,000 soldiers even to know who they were.

In a single battle on a single day, Britain had lost more soldiers than in the first four months of the war: the amount was just short of the 21,000 who died in the three years of the Boer War and more than four times the number of British servicemen and women who have lost their lives in the line of duty since the end of the Second World War.

Current historians are inclined to frame the Somme as an essential stepping-stone to winning the war, even to conclude that the sacrifice of July 1 was ‘justified’ by the Allies’ eventual victory. Such assessments might have offered some consolation to the grieving yet still jingoistic millions of 1916. They would have meant less 10 years later. In the decades that followed the Armistice, it appeared to a shattered nation that the only result of the Somme and its opening day (like the ‘Great’ War they came to symbolise) was death and untellable suffering on a scale it had never known; their only purpose, to be remembered. A hundred years later, the purpose seems the same.

The last surviving soldiers of the trenches have been gone for nearly a decade. Even the grandsons of those who grieved are getting old. But while the First World War must slowly recede in our collective memory, it seems likely that the story of the middle day of its middle year never will.

The 14 original, hand-annotated ‘Zero Hour’ panoramas are to be exhibited at the Sladmore Contemporary Gallery, London W1, from July 1 to 15 (www.sladmorecontemporary.com)

Poster prints of the ‘Zero Hour’ panoramas can be ordered at www.jolyonfenwick.com

‘Zero Hour: 100 years on: Views from the Parapet of the Somme’ is published by Profile Books (£25).