Joe Sacco's The Great War – in pictures

Most of the men sent to the Somme are New Army volunteers. At the height of every recruitment, 30,000 men enlisted each day Photograph: Joe Sacco

As night falls, an Indian cavalry unit moves up close to the front line. Three divisions of cavalry are positioned to exploit the expected breakthrough and gallop into the open ground behind the German lines Photograph: Joe Sacco

The bombardment lifts from the German front line and switches to positions further back ... the men are ordered to advance at a walking pace toward the German lines ... some units have been told they are unlikely to find a live German Photograph: Joe Sacco

Germans who have survived the bombardment leave their deep dugouts and begin machine-gunning the rows of British troops … a German barrage on to no-man's land begins … the German barrage lands on the British positions. Many soldiers are killed or wounded before they even leave the trenches Photograph: Joe Sacco

The walking wounded must make their own way back to a casualty clearing station. Stretcher cases are transported there by motorised or horse ambulances Photograph: Joe Sacco

Those who have died at the casualty clearing station are buried nearby. Twenty-one thousand men have been killed outright in the attack or would die of their wounds Photograph: Joe Sacco