On the publication in March 1812 of his long narrative poem “Childe Harold’s Pilgrimage”, Lord Byron, heady with self-celebration, wrote: “I woke one morning and found myself famous.”

Edward Thomas, the Anglo-Welsh poet and essayist who was killed, aged 39, on the western front in the spring of 1917, had no such sense of instant and ecstatic recognition. For most of his adult life he laboured fretfully as a book reviewer and hack writer, hustling for commissions to support his free-thinking wife Helen and their three children. Sometimes suicidal and often stricken by depression – he was diagnosed as a “neurasthenic” in the opaque psycho-pathological terminology of the day – he longed to be liberated from the drudgery of a life spent writing about writing. He felt caged by domesticity and would, at various times, choose to spend long periods apart from his wife and children, whom he loved but neglected and mistreated. “What I really ought to do is live alone,” he confessed to a friend. “It is really the kind H [Helen] and the children who make life almost impossible.”

At such times Thomas’s melancholy can feel unearned, the self-pity of a man of letters who married and became a father too young, as an undergraduate at Oxford, and who was obliged to work. “For I hate my work,” he wrote, “my reviewing: my best I feel is negligible: I have no vitality, no originality, no love. I do harm. Love is dead and lust almost dead.”

In spite of his sense of failure and exaggerated self-reproach, Thomas was an influential and strenuous critic of poetry, the literary form he revered above all others, and a friend of many other writers, including Rupert Brooke and Joseph Conrad. He was tall and attractive, liked and admired by many. His life was interesting and varied as he moved between the family cottage in rural Hampshire and literary London.

None of this was enough for him, however, because he yearned to write not criticism, travel guides or biography, but his own “original writing”, as he called it. What he wanted above all else was to write poetry. It was not until he met and became friends with the American poet Robert Frost at a gathering in London that he began tentatively to believe it would be possible for him to write poetry rather than merely to review it.

Frost was four years older than Thomas and moved to England, on a whim, in 1912. The two men shared an interest in what the American called the “sound of sense”: poetry that, in its metrical pattern, aspires to the condition, naturalness and rhythms of speech. Though Matthew Hollis makes much of the influence of the friendship on both men, in Now All Roads Lead to France it’s clear that without the encouragement of Frost, Thomas would never have found his poetic voice. But without Thomas, you feel, Frost would have been just fine; he was already publishing poetry before he moved to England and was the more confident and self-assertive of the two, a raconteur and teacher.

As you would expect of a professional poet, Hollis is preoccupied with the micro world of the London poetry scene in the years immediately preceding the first world war, with its various factions and divisions between Georgians and Imagists, rather than with the macro world of politics and international affairs. He monitors the gathering storm in the southern Balkans only out of the corner of his eye and says very little about the wider socio-political context in which Thomas operated.

Thomas’s father was a Lloyd George Liberal who was committed to home rule for Ireland but that doesn’t interest the author. Instead, he writes at length about poets now mostly forgotten or little read, all friends of Thomas, and quotes extensively from old reviews, recounting who said what about whom and in which publication and when. Does any of this matter?

What matters is the poetry Thomas belatedly started to write towards the end of 1914 and beyond. The book enlarges and quickens with the onset of the war as Thomas begins to agonise and equivocate over whether he should enlist, as Rupert Brooke had (conscription was introduced in 1916), or follow Frost back to America. He felt conflicted. He was patriotic but appalled by jingoism; he loved the countryside about which he wrote so poignantly and knew that while he prevaricated, others were prepared to act to defend an ideal of England.

On long walks with Frost, he discussed what he should do and was troubled by what he considered to be his lack of courage. Then, one day, with Frost having returned to America, Thomas received from his friend in the post a draft of what would become “The Road Not Taken”, one of his most celebrated poems. Thomas read its narrative of choice and missed opportunities as a direct challenge; within days of receiving it he had enlisted in the Artists Rifles, a volunteer regiment of the British army.

The first world war has been called the English Holocaust. Few would disagree with historian John Keegan’s declaration that it “damaged civilisation, the rational and liberal civilisation of the European enlightenment, permanently for the worse”. Thomas’s poems – like those of Wilfred Owen, Ivor Gurney, Edmund Blunden and others – have helped to define the way in which the war has been represented and how, today, it is remembered and understood.

Thomas is a fine yet modest poet of nature; a delicate chronicler, often in blank verse, of landscape, rural life and the ever-changing English weather. His best-loved poem, “Adlestrop”, recalls a moment when a train on which he was travelling unexpectedly stopped at a station in the Cotswolds. These are the last days of the last summer before the war. From the train the poet sees “willows, willow-herb, and grass,/ And meadowsweet, and haycocks dry”. And in the closing lines it’s as if the poem dissolves into birdsong: “And for that minute a blackbird sang/Close by, and round him, mistier,/ Farther and farther, all the birds/ Of Oxfordshire and Gloucestershire.” Even during battle in France, Thomas never lost his heightened receptivity to nature or his gift for noticing the movement of a thrush or the effects of sunlight on frost.

Hollis writes gracefully, and with great empathy, about Thomas’s sad struggles and yearnings. His absorbing, rather old-fashioned book, which reminds me, in tone and sensibility, of Robert Gittings’ 1969 biography of John Keats, serves as a tribute to one of poetry’s more suffering souls. It’s also an evocation of a lost England that Thomas himself elegised so movingly in the nature poems that, although almost all unpublished in his lifetime, have found an enduring place in the canon of English literature.