Western Front (World War I)
Battle of the Somme

In the spring, Allied commanders had been concerned about the ability of the French Army to withstand the enormous losses at Verdun. The original plans for an attack around the River Somme were modified to let the British make the main effort. This would serve to relieve pressure on the French, as well as the Russians who had also suffered great losses. On 1 July, after a week of heavy rain, British divisions in Picardy began the Battle of the Somme with the Battle of Albert, supported by five French divisions on their right flank. The attack had been preceded by seven days of heavy artillery bombardment. The experienced French forces were successful in advancing but the British artillery cover had neither blasted away barbed wire, nor destroyed German trenches as effectively as was planned. They suffered the greatest number of casualties (killed, wounded and missing) in a single day in the history of the British Army, about 57,000.

The Verdun lesson learnt, the Allies' tactical aim became the achievement of air superiority and until September, German aircraft were swept from the skies over the Somme. The success of the Allied air offensive caused a reorganisation of the German air arm and both sides began using large formations of aircraft rather than relying on individual combat. After regrouping, the battle continued throughout July and August, with some success for the British despite the reinforcement of the German lines. By August, General Haig had concluded that a breakthrough was unlikely and instead, switched tactics to a series of small unit actions. The effect was to straighten out the front line, which was thought necessary in preparation for a massive artillery bombardment with a major push.

The final phase of the battle of the Somme saw the first use of the tank on the battlefield. The Allies prepared an attack that would involve 13 British and Imperial divisions and four French corps. The attack made early progress, advancing 3,200–4,100 metres (3,500–4,500 yd) in places but the tanks had little effect due to their lack of numbers and mechanical unreliability. The final phase of the battle took place in October and early November, again producing limited gains with heavy loss of life. All told, the Somme battle had made penetrations of only 8 kilometres (5 mi) and failed to reach the original objectives. The British had suffered about 420,000 casualties and the French around 200,000. It is estimated that the Germans lost 465,000, although this figure is controversial.

The Somme led directly to major new developments in infantry organisation and tactics; despite the terrible losses of 1 July, some divisions had managed to achieve their objectives with minimal casualties. In examining the reasons behind losses and achievements, once the British war economy produced sufficient equipment and weapons, the army made the platoon the basic tactical unit, similar to the French and German armies. At the time of the Somme, British senior commanders insisted that the company (120 men) was the smallest unit of manoeuvre; less than a year later, the section of ten men would be so.
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