Sassoon was educated at the New Beacon School, Sevenoaks, Kent then Marlborough College, Wiltshire and finally at Clare College, Cambridge, where from 1905 to 1907 he read history. He went down from Cambridge without a degree and spent the next few years indulging himself hunting, playing cricket and writing verse.
However, motivated by patriotism, Sassoon joined the Sussex Yeomanry of the British Army as the threat of war escalated into open conflict.
His early poems exhibit a Romantic, dilettantish sweetness but his war poetry moves to an increasingly discordant beat, stridently conveying the ugly truths of the trenches to an audience hitherto placated by jingoistic and patriotic propaganda.
Sassoon's periods of duty on the Western Front were marked by near-suicidal missions, including the single-handed capture of a German trench. Armed with grenades, he scattered sixty German soldiers.
In 1919 took up a post as literary editor of the socialist Daily Herald. Here he was responsible for employing several eminent reviewers, including E. M. Forster and Charlotte Mew. Sassoon also commissioned new material from the likes of Arnold Bennett and Osbert Sitwell.
Sassoon was now, in 1928, preparing to take a new direction by branching out into prose, with 'Memoirs of a Fox-Hunting Man'. This anonymously published first volume of a fictionalised autobiography, was acclaimed as a classic, bringing its author fame as a humorous writer. Other volumes including his own autobiography based on his youth and early manhood across three volumes followed.
In his last years Sassoon converted to Roman Catholicism and was admitted to the faith at Downside Abbey in Somerset.
Siegfried Loraine Sassoon, CBE, MC died from stomach cancer on 1st September 1967, a week before his 81st birthday.