How was Wilfred Owen's "Dulce Et Decorum Est" influential in the Modernist movement?

I think the answer to this question lies in the focus of
this awesome poem and the realistic way in which it is written. Let us remember that a
key and central event that fed into what we know as Modernism was the Great War, or
World War I, which, through the way in which old values of national honour and glory had
resulted in a war that resulted in massive loss of life, created a sense of
disillusionment and pessimism and a new realism. Thus we can see this poem as capturing
some of the key elements of this movement through the way it acts as a reaction to
romantic notions of war and honour and patriotism through its presentation of the grim
realism of what soldiers actually endured.

If you look at
the very first line of the poem, Owen does much to strip away any idea or impression of
war's grandeur. We have a picture in our mind of soldiers as being all dressed in
uniform and being strong, young men, proud to fight for their country. The first line
presents the soldiers as being "like old beggars under sacks" and "coughing like hags."
They are so exhausted that they are "Drunk with fatigue." When death comes, it is not at
the hands of an opponent that the soldier has met in battle, it is impersonal, distant,
and indiscriminate. In addition, the manner of death is horrific as the gas is shown to
torture him. Note the description of the body that we are
given:

And
watch the white eyes writing in his face,

His hanging face,
like a devil's sick of sin;

If you could hear, at every
jolt, the blood

Come gargling from the froth-corrupted
lungs...

Nothing is spared in
the hideous description that we are given to communicate the way in which such notions
of heroism and patriotism are actually lies. Thus the poem remains an important example
of Modernist poetry through its realistic and pessimistic presentation of the realities
of war.