The first day of the Somme offensive was the bloodiest in the history of the British Army. More than 20,000 were killed and 60,000 injured. Sixty per cent of all the officers were also killed on the first day.

The offensive, which took place between 1 July and 18 November 1916, was intended as a decisive breakthrough for the allies. Instead it became a slow battle of attrition which led to more than a million casualties.

It was also a baptism of fire for the new armies of volunteers who responded to Lord Kitchener's appeal to join up in 1914.

The Somme was originally intended as a heavy attack from the south by the French, with British making a diversionary attack to the north.

But the battle of Verdun had used up so many French divisions that when the attack was launched it was the British who undertook the main assault.

The main British effort took place along the line of the river Somme which marked he junction of the British and French armies. The British attack was towards Baupaume on a 15-mile front and the French towards Peronne on a 10-mile front.

After an eight-day preliminary bombardment, in which nearly 1.7 million shells were fired at German positions, the allies attacked. But the shells were often of poor quality and failed to destroy German dugouts.

Although the British came under heavy fire the French quickly broke through the German lines. Haig sent the newly formed Fifth army to help hold the gains made by the French.

For the next 10 weeks little headway was made in the battle. Both the British and the French constantly shelled the Germans and making a few costly gains.

The British Commander-in-Chief, Sir Douglas Haig's use of what many criticised as flawed tactics caused controversy. In Britian it contributed to the first signs of war-weariness.

Haig was determined to batter his way through the German lines and on 15 September he renewed the British offensive - this time using tanks for the first time in battle. They helped to increase the allied penetration even though half of them failed to start due to mechanical problems.

The battle finally ended on 19 November with an area approximately 25 miles long by six miles wide won by the allies. After four months of fighting each side had sustained more than half a million casulaties.