Battle of the Somme
The Battle of the Somme was an Allied offensive during World War I on the western front. It was launched in early July, 1916. The first day was the single bloodiest day in British military history.
The offensive was timed to relieve pressure from the Battle of Verdun.
The British attacks went over the top with insufficient artillery support and the infantry ran into uncut barbed wire entanglements. German artillery and machine guns caused tremendous casualties. Many units were almost completely wiped out, and because some of them were recruited from the same towns, many towns across Britain were particularly traumatized by this battle. Units from the British Empire also participated, including Canada, South Africa, Australia, New Zealand, India, and the West Indies (in a supporting role). The Allies advanced around seven miles at great cost, a nearly meaningless gain in territory because the Germans retreated to the more defensible Hindenburg Line the next year.
Widely recognized as a catastrophe for nearly a century, recent historians have begun offering opinions that the Somme was a British victory in that it caused many German casualties and forced the British to improve their battlefield tactics. This neglects the fact that the Allies quite probably would have lost the war in 1918 because their manpower reserves were exhausted, if not for the intervention of the United States. On a larger level, the loss of so many men was a blow to the British Empire that it never recovered from, leading to an inability to prevent World War II or decolonization.