One of the bloodiest clashes of the First World War, the five-month battle of the Somme claimed the lives of more than 127,000 British soldiers, with more than 57,000 British casualties on the first day alone. Here, on its 100th anniversary, Anthony Richards, head of documents and sound at Imperial War Museums (IWM), reveals eight lesser-known facts about Britain’s most famous battle.

1) The battle of the Somme was an Anglo-French campaign

While 1916’s summer offensive would be an Anglo-French collaborative attack, the French remained the dominant partner with more men in the field and arguably a greater stake in the war: to them it remained, after all, a question of liberating their own ground as well as addressing the wider issue of German aggression. It would therefore be the French commander-in-chief, General Joffre, who would control the overall direction of the campaign.

Picardy was the area chosen for the attack, in the sector where the French and British armies adjoined each other on either side of the river Somme. The French would launch an attack south of the river while the British would attack to the north, both armies sharing a huge battlefront that was initially intended to span some 60 miles. No major offensive had yet taken place in the Somme sector and the surrounding ground had therefore escaped the wholesale destruction that other areas of France and Belgium had suffered.

One of the benefits to Joffre of a joint Anglo-French offensive was that he could ensure that both armies would stay resolute to the overall military agenda and prevent any postponements. Haig, as well as many of the other British commanders, actually favoured an offensive in Belgium so that the strategically important coastline could be liberated and controlled. Preservation of Britain’s alliance with the French was crucial, however, if any long-term success was to be achieved against Germany.

But in the event, it would prove to be neither Joffre nor Haig who made the most important decision ahead of the battle. The agenda was ultimately controlled by the Germans, when they launched a major attack on the French fortress city of Verdun on 21 February 1916.

2) It was never intended as the battle to finish the war

The unexpected German attack on Verdun [in February 1916] and resultant drain on French resources meant that the British role would now be the more dominant one in the Anglo-French plan. Perhaps unusually, there were no major strategic objectives to the battle, although Haig's intentions for the offensive were clear.

My policy is briefly to: 1. Train my divisions, and to collect as much ammunition and as many guns as possible. 2. To make arrangements to support the French... attacking in order to draw off pressure from Verdun, when the French consider the military situation demands it. 3. But, while attacking to help our Allies, not to think that we can for a certainty destroy the power of Germany this year. So in our attacks we must also aim at improving our positions with a view to making sure of the result of the campaign next year.

The Somme was therefore never intended as “the battle to end the war”, but rather as an offensive to put the British and French in a better position by the end of 1916. While the concept of a ‘big push’ in the summer months was fully expected by all and undoubtedly intended to be a decisive action in the course of the conflict, it is important to remember that for the British and French high commands, the battle of the Somme was always envisioned to be a step towards the end of the war rather than a definite conclusion to it.

3) The date of the attack was much debated

With Sir Douglas Haig and his staff now based at their general headquarters established in the chateau at Montreuil, a meeting on 26 May finalised the date of the Somme attack. Joffre insisted that 1 July should be the absolute latest day for the offensive to begin, since the French were suffering under the continued German assault on Verdun and desperately required the pressure on them to be diverted elsewhere. While Haig tried to argue for a later date in August, in order to allow greater time for the British to prepare themselves for such a major attack, this proved unrealistic when faced with the immediate need to support the French. A compromise of Thursday 29 June was therefore decided upon.

With artillery bombardments remaining the key to success in any offensive, the use of aircraft and observation balloons to guide them was considered crucial. This co-operation was very much a developing skill, however, and the Somme would prove to be a baptism of fire for both the Royal Flying Corps and artillery. Right up to the final days of June, bombing raids were organised in order to hit rear areas behind the German lines that were unreachable by even the longest-range British guns. However, deteriorating weather towards the end of the month meant that bombing and observation work by the RFC was impeded, in turn affecting the accuracy of the artillery barrage. This led to the date of the main infantry attack being put back slightly to Saturday 1 July.

4) The infantry attack was preceded by the detonation of mines

Minutes before Zero Hour [7.30am] on 1 July, mines that had been carefully prepared by the Royal Engineer tunnelling companies over the past few weeks were finally detonated. British tunnellers had been busy digging such mines deep beneath the German defences, which were packed with ammonal explosive for detonation at the appointed hour. Secrecy in such operations was essential, as the Germans could be heard digging their own mines close by, and the element of surprise had to be maintained at all costs.

At 7.20am, the 40,600lb mine was fired under Hawthorn Ridge in the northern sector between Beaumont-Hamel and Serre, while eight minutes later others were detonated near La Boisselle (the 60,000lb Lochnagar and 40,600lb ‘Y Sap’ mines), opposite Fricourt (the Triple Tambour mine), and between Mametz and Montauban (the Kasino Point mine).

However, despite the impressive spectacle they generated, the explosions provided little practical advantage. Their effect was too localised, with German machine guns and artillery in the surrounding areas being moved in quickly to fill the defensive gaps. Indeed, in the case of the Hawthorn Ridge explosion, which was mistimed to detonate 10 minutes before the infantry attack, the Germans were given a clear warning of the impending assault, allowing them to be poised and ready to meet their attackers.

5) Many British infantry walked into battle

7.30am on 1 July 1916 was marked by the sound of whistles being blown by British officers all along the front line, signalling the start of the infantry assault. The soldiers emerged from their trenches, climbed over the parapet and began to advance, the British artillery having extended the range of their guns to concentrate on the German reserve lines.

Army orders had specified that the men should advance at a steady walking pace in long lines, two or three yards apart. Many senior commanders believed that the inexperienced new volunteer soldiers would be unable to cope with more sophisticated tactics, while such a tight formation would ensure that they arrived at the German line at the appropriate time. There was no need for haste, since it was expected that most of the German defences had already been destroyed by the artillery bombardment.

Further waves of men followed every hundred yards or so, their purpose being to help overcome any blockages before consolidating the target objectives. This plan was chiefly followed despite some local variations in areas of the front where more experienced officers chose to adopt a more mobile form of attack.

6) 1 July 1916 proved to be the most disastrous day in the history of the British Army

57,470 British casualties were sustained during the course of 1 July 1916, comprising 35,493 wounded and 19,240 killed. Casualties were high across all units, but some battalions were almost annihilated: the 10th Battalion of the West Yorkshire Regiment alone lost more than 700 men of all ranks. German counterattacks during the afternoon recaptured much lost ground north of the Albert–Bapaume road. Only to the south were results somewhat more successful, with attacks on the villages of Fricourt and Mametz.

While it would be easy to criticise the British attackers, who in many cases lacked experience and training, insufficient artillery was also a factor. Although shells were now being supplied to the front in high numbers, they were extremely variable in quality, with many wavering in flight and others failing to explode on impact. Some historians have also highlighted the 66 pounds of kit being carried by many of the British troops which weighed them down, affecting their speed and mobility. However, some units chose to discard any unnecessary equipment before attacking, based on the experience and common sense of individual officers.

But the key factor was the notable strength of the German defences. The Germans had made considerable advances in the design and construction of bunkers and strong points that protected them during the British bombardment. Once the barrage lifted, both men and guns emerged to wreak havoc on their attackers.

The immediate breakthrough that Haig had hoped for had not been achieved, yet despite the terrible slaughter to the left of the line, some advances had been made to the right as well as in the French sector further to the south. The battle would continue over the coming months but rather as a more staggered attack which, over time, would become a war of attrition.

7) The Somme saw the first use of armoured tanks

From very early on in the war, a clear need was established for an armoured car of some kind in order to cross the uneven ground of no man's land, ride over barbed wire and assault strongpoints with its onboard weaponry. An Admiralty Landships Committee was established in February 1915 in order to construct the initial prototypes. The armoured vehicles were soon christened as ‘tanks’ during production, reflecting their initial similarity to steel water tanks but chiefly to maintain secrecy over their ultimate purpose.

Originally intended to lead the 1 July assault, delays in their production meant that it was not until September that a suitable number of vehicles could be supplied, and this would only be a rather limited 49. In the event, only 32 tanks made their starting positions for the battle of Flers-Courcelette on 15 September, in which their objective would be to move ahead of the attacking infantry and assist in suppressing identified strong points.

The infantry advanced behind a creeping barrage, with tanks accompanying them into battle. Just over half the number of tanks that trundled into no man’s land as part of the main advance managed to reach the German lines, although many of these demonstrated success in crushing the barbed wire defences, protecting the British infantry and, perhaps most notably, boosting the morale of the attackers while generating uncertainty among the German defence.

But they were extremely unreliable, breaking down continually, and they were too slow to really spearhead any attack, while their crews lacked both training and experience. Artillery was still seen as the deciding factor in any attack, with the tank simply a new novelty to be fitted in where it could. Despite their limitations, however, Haig was impressed with the new vehicles, and production of tanks on a grand scale would begin in January 1917.

8) Final casualty figures

The cost in lives due to the battle of the Somme was enormous. While 1 July 1916 has gone down in history as the worst day for the British Army in terms of the casualty figures sustained and the limited objectives achieved, it was the ongoing battle throughout the subsequent five months that should not be forgotten. During the entire campaign, the casualty figures were staggering: the numbers for German casualties on the Somme vary, but between 500,000 and 600,000 soldiers were killed, missing or captured. The French suffered 204,253 total casualties, and the British 419,654. Of this number, some 127,751 British soldiers died between 1 July and 20 November 1916, at an average of 893 per day.

Over the past century the battle of the Somme has been regarded by many in Britain and her former empire as symbolic of the slaughter of the First World War, with the first day in particular seen as a terrible highpoint for casualties, but in reality the French had endured far worse. On 22 August 1914, for instance, they had suffered 27,000 killed in a single day, while the ongoing war of attrition at Verdun had created their own national synonym for bloodshed and sacrifice. The German Army suffered the greatest number of casualties, perhaps reflecting the determination shown by the defenders in holding their positions in the face of such an onslaught.

But the incredible sacrifice made by British soldiers has ensured the Somme’s continuing role in the collective memory of the nation.

Anthony Richards is head of documents and sound at Imperial War Museums (IWM) and author of the IWM’s new book The Somme: A Visual History, which is out now. From photographs to artworks, film to posters, this new book explores the battle of the Somme through the extensive IWM collections.