The Battle of the Somme, also known as the Somme Offensive, takes place during the First World War between 1 July and 18 November 1916 on either side of the river Somme in France.

The battle sees the British Army, supported by contingents from British imperial territories, including Australia, New Zealand, Newfoundland, Canada, India and South Africa, mount a joint offensive with the French Army against the German Army, which has occupied large areas of France since its invasion of the country in August 1914.

The Battle of the Somme is one of the largest battles of the war; by the time fighting pauses in late autumn 1916, the forces involved have suffered more than 1 million casualties, making it one of the bloodiest military operations ever recorded.The plan for the Somme offensive evolves out of Allied strategic discussions at Chantilly, Oise in December 1915.

Chaired by General Joseph Joffre, the commander-in-chief of the French Army, Allied representatives agree on a concerted offensive against the Central Powers in 1916 by the French, British, Italian and Russian armies.

The Somme offensive is to be the Anglo-French contribution to this general offensive and is intended to create a rupture in the German line that could then be exploited with a decisive blow.

With the German attack on Verdun on the River Meuse in February 1916, the Allies are forced to adapt their plans.

The British Army takes the lead on the Somme, though the French contribution remains significant.The opening day of the battle sees the British Army suffer the worst day in its history, sustaining nearly 60,000 casualties.

Because of the composition of the British Army, at this point a volunteer force with many battalions comprising men from particular localities, these losses (and those of the campaign as a whole) have a profound social impact.

The battle is also remembered for the first use of the tank.

At the end of the battle, British and French forces have penetrated 6 miles (9.7 km) into German occupied territory, with the British Army still three miles (5 km) from Bapaume, a major objective.

The German Army maintains its frontl ine over the winter of 1916-17, before withdrawing from the Somme battlefield in February 1917 to the fortified Hindenburg Line.The conduct of the battle has been a source of controversy: senior officers such as General Sir Douglas Haig, the commander of the British Expeditionary Force and Henry Rawlinson, the commander of Fourth Army, have been criticized for incurring very severe casualties while failing to achieve their territorial objectives.

Other historians have portrayed the Somme as a preliminary to the defeat of the German Army and one which taught the British Army tactical and operational lessons.