Seventy years ago, the poet Keith Douglas was killed during the Allied invasion of Normandy on 9 June, three days after D-Day. He was 24.

Douglas had shown a talent for poetry since childhood – as well as a passion for all things military. At Oxford, where he was taught for a time by Edmund Blunden, he already knew his task as a poet: it was to fuse the "cynic and lyric" aspects of his nature to form "a balanced style". If he admired the first world war poets, he was determined not to follow their path with protests and pity. Such writing, as he said, would have been "tautological".

While serving in the north African campaign Douglas was wounded by a mine. This week's poem, Desert Flowers, was probably written while he was recovering in El Ballah General Hospital, Palestine, early in 1943.

It's more introspective than Vergissmeinnicht or How to Kill – the famous, ground-breaking poems he wrote a little later. Yet it's hardly atypical. The same clear-voiced speaker, idiomatic and direct, utters thoughts aloud – in this case, not only to himself, but for the attention of a fellow poet. In fact, Isaac Rosenberg, killed in 1918, is the first world war poet whose "cynic-lyric" style is closest to Douglas's own.

Succinct but mysterious, Desert Flowers belongs to a liminal state between sleeping and waking, night and day. It seems to open and close: first, to look outwards at the "wide landscape" and then to turn to the unconscious desires where poetry – even the starkest war poetry – is generated. There's a convalescent quality of memories being reviewed in quiet darkness, and energies gathered.

Douglas admitted he was no naturalist. He described the flowers he saw in the fertile patches of Nofilia as "an indeterminate sort" and mostly mauve and yellow, although he did identify "veritable daises and dandelions". The flowers in the poem are real but known only by one un-decorative adjective – "hungry". They are fed by dead bodies (the word "fill" in line five, one of several Biblical echoes in the poem, reminds us that God "filled the hungry with good things, and the rich he sent empty away"). Men, animals and flowers alike participate in natural, predatory processes. The shell is not entirely dissimilar to the hawk. The dogs are humanised, and "cry words / at nights". The landscape evoked is bigger than the human battlefield: it's an entire ecological system.

In lines six and seven, it's not clear whether the dogs, the words or the nights are "the most hostile things of all". Since "night" is personified later through "draperies", and "dogs" simply belong to the guiltless order of predation, "words" are the most likely culprits. Such a reading connects to the earlier description of the effect of the shells, slaying not only men and jerboas, but "the mind" – the factory of words. Words are difficult to find and keep, under such pressure. Similarly, dead men and blasted trees, and "the detail and the horizon", become confused.

"My gods the dead possess my soul," Douglas wrote in an earlier poem. When the speaker looks "each side of the door of sleep / for the little coin … " the reader first thinks of the coin required, in classical mythology, to pay for transport to the underworld. But this coin has an extra value: on the way, it will "buy the secret I shall not keep". It will buy, in effect, the truthful poem. "Suffering" and "sing" rhyme daringly, in the last stanza, though not as dangerously as the rhyme of "horizon" and "set eyes on". The effect could hardly be less comic. Desert Flowers clarifies the relationship of death and poetic perfection for Douglas. He seems to know he is within sight of both.

Desert Flowers

Living in a wide landscape are the flowers –

Rosenberg I only repeat what you were saying –

the shell and the hawk every hour

are slaying men and jerboas, slaying

the mind: but the body can fill

the hungry flowers and the dogs who cry words

at nights, the most hostile things of all.

But that is not news. Each time the night discards

draperies on the eyes and leaves the mind awake

I look each side of the door of sleep

for the little coin it will take

to buy the secret I shall not keep.

I see men as trees suffering

or confound the detail and the horizon.

Lay the coin on my tongue and I will sing

of what the others never set eyes on.