Question: Who one of the leading poets of the First World War, who was the first known user of the phrase  "the pity of war" ?

Context articles: The Pity of War
Futility (poem)
Wilfred Owen
Lions led by donkeys
Anton Schnack
Netherwood Hughes
Siegfried Sassoon
Kenneth Slessor
British women's literature of World War I
The Muse in Arms

The first known use of the phrase "the pity of war" was by Wilfred Owen in 1918, in the preface to his collected poems, which would be posthumously published.
 The phrase, has been used as a title of books and other media over a long period.
"Futility" is a poem written by Wilfred Owen, one of the most renowned poets of World War I.
 The poem was written in May 1918 and published as no. 153 in "The Complete Poems and Fragments".
 The poem is well known for its departure from Owen's famous style of including disturbing and graphic images in his work; the poem instead having a more soothing, somewhat light-hearted feel to it in comparison.
 A previous secretary of the Wilfred Owen Association argues that the bitterness in Owen's other poems "gives place to the pity that characterises his finest work".
 Futility details an event where a group of soldiers attempt to revive an unconscious soldier by moving him into the warm sunlight on a snowy meadow.
 However, the "kind old sun" cannot help the soldier - he has died.
Wilfred Edward Salter Owen, MC (18 March 1893 – 4 November 1918) was an English poet and soldier, one of the leading poets of the First World War.
 His war poetry on the horrors of trenches and gas warfare was heavily influenced by his mentor Siegfried Sassoon, and stood in stark contrast both to the public perception of war at the time and to the confidently patriotic verse written by earlier war poets such as Rupert Brooke.
 Among his best-known works – most of which were published posthumously – are "Dulce et Decorum est", "Insensibility", "Anthem for Doomed Youth", "Futility", "Exposure" and "Strange Meeting".
"Lions led by donkeys" is a phrase popularly used to describe the British infantry of World War I and to blame the generals who led them.
 The contention is that the brave soldiers (lions) were sent to their deaths by incompetent and indifferent leaders (donkeys).
 The phrase was the source of the title of one of the most scathing examinations of British First World War generals, The Donkeys—a study of Western Front offensives—by politician and writer of military histories Alan Clark.
 The book was representative of much of the First World War history produced in the 1960s and was not outside the mainstream—Basil Liddell Hart vetted Clark's drafts—and helped to form a popular view of the First World War (in the English-speaking world) in the decades that followed.
 However, the work's viewpoint of incompetent military leaders was never accepted by some mainstream historians, and both the book and its viewpoint have been subject to attempts at revisionism.
Anton Schnack (21 July 1892 – 26 September 1973) was a German writer.
 He joined the German Army when World War I began.
 He is one of the leading German war poets of the First World War, and has been compared with English poet Wilfred Owen.
 After the war he became an editor for numerous publications.
 He was one of the 88 writers who pledged their allegiance to Adolf Hitler in October 1933 in a Vow of Most Faithful Allegiance (Gelöbnis treuester Gefolgschaft).
Netherwood "Ned" Hughes (12 June 1900 – 4 April 2009) was one of the last two Tommies who served the United Kingdom during the First World War, along with Harry Patch, although Patch was the only one to have seen action.
 Hughes was also one of three British veterans still living in the country, with Patch and Henry Allingham being the other two.
 The Ministry of Defence has not confirmed his war service, but many First World War service records were destroyed in the Blitz during the Second World War.
 However the World War I Veterans Association invited him to the Cenotaph for the 90th Anniversary of the Armistice.
 He did not attend as his family felt that the journey would be too much for him.
Siegfried Loraine Sassoon, {'1': ", '2': ", '3': 'CBE, MC', '4': "} (8 September 1886 – 1 September 1967) was an English poet, writer, and soldier.
 Decorated for bravery on the Western Front, he became one of the leading poets of the First World War.
 His poetry both described the horrors of the trenches, and satirised the patriotic pretensions of those who, in Sassoon's view, were responsible for a jingoism-fuelled war.
 Sassoon became a focal point for dissent within the armed forces when he made a lone protest against the continuation of the war in his "Soldier's Declaration" of 1917, culminating in his admission to a military psychiatric hospital; this resulted in his forming a friendship with Wilfred Owen, who was greatly influenced by him.
 Sassoon later won acclaim for his prose work, notably his three-volume fictionalised autobiography, collectively known as the "Sherston trilogy".
Kenneth Adolphe Slessor {'1': ", '2': ", '3': 'OBE', '4': "} (27 March 190130 June 1971) was an Australian poet, journalist and official war correspondent in World War II.
 He was one of Australia's leading poets, notable particularly for the absorption of modernist influences into Australian poetry.
 The Kenneth Slessor Prize for Poetry is named after him.
For much of the twentieth century, a deep ignorance was displayed towards British women’s literature of World War I.
 Scholars reasoned that women had not fought combatively, thus, did not play as significant a role as men.
 Accordingly, only one body of work, Vera Brittain’s autobiographical, "Testament of Youth", was added to the canon of Great War literature.
 Conversely, anthologies published mid-century such as Brian Gardner’s, "Up the Line to Death: The War Poets of 1914-1918", contained no mention of contributions made by women.
 Similarly, Jon Silkin’s 1979 anthology, "Penguin Book of First World War Poetry", included the work of only two women, Anna Akhmatova and Marina Tsvetaeva.
 However, new research has changed ideological beliefs about the role women assumed in producing authentic accounts of war.
 More specifically, in Britain, research attends to an explanation of how women’s war literature shaped feminist discourse during and immediately following the war.
The Muse in Arms is an anthology of British war poetry published in November 1917 during World War I.
 It consists of 131 poems by 52 contributors, with the poems divided into fourteen thematic sections.
 The poets were from all three branches of the armed services, land, sea and air, from a range of ranks (though mostly officers) and from many parts of the UK.
 Twenty of the poets who contributed to this volume died during the war.
 The editor was the journalist and author Edward Bolland Osborn (1867–1938), and the book was printed in London by the publishers John Murray.
 This anthology was one of several collections of war poetry published in the UK during the war.
 It "achieved large sales", and was reprinted in February 1918.
 It has been referenced in several analyses of First World War poetry and has been described as "the most celebrated collection of the war years".