Five writers explore the year 1917 through the work of five Great War artists. Tonight, Joanna Bourke on Siegfried Sassoon and his celebrated protest against the conflict.

"I am making this statement as an act of wilful defiance of military authority, because I believe that the War is being deliberately prolonged by those who have the power to end it." So wrote the soldier-poet Siegfried Sassoon in July 1917, in a letter to the Times newspaper. "I am a soldier," he went on, "convinced that I am acting on behalf of soldiers. I believe this War, upon which I entered as a war of defence and liberation, has now become a war of aggression and conquest." The result was uproar - and Sassoon's subsequent confinement to Craiglockhart Hospital in Edinburgh, suffering (the authorities concluded) from shell-shock.

In tonight's Essay, Joanna Bourke re-reads Sassoon's letter of protest and examines what led up to his outspoken anti-war declaration, and what happened next.

Producer: Simon Elmes.