tell that this poem is a condemnation of war.

Wilfred Owen served on the front lines in the British army. He knew the horrors of war first hand. He also knew that fighting in the conflict was being touted as a glorious and patriotic duty by those in Britain. This poem, and many of his other works as well, was written to stand in contrast to the propaganda on the home front. In "Dulce et Decorum Est,"Owen highlights the terror and agony of a gas attack. He describes a soldier drowning under the fumes of the gas, terrified and helpless. He describes how this image haunts the survivors. This soldier's death was a senseless one. He did not die upon the glorious battlefield. He died in misery and his death accomplished nothing.

Prior to this period, poets often glorified war. Their words inspired many young men to risk their lives for king and country. This poem is a rebuke to these poets of the past. Owen wants to make it clear that no one who actually witnessed these senseless horrors would ever encourage anyone with tales of glorious sacrifice.

In Wilfred Owen’s poem “Dulce et Decorum Est,” war is portrayed as a hellish experience devoid of traditional notions of glory and honor. Owen, himself a soldier on the Western Front when he was writing, knew the nightmares of the trenches first-hand and sought to reveal the truth of the war through his poetry.

Owen’s first-person poem is divided into three stanzas. The first two stanzas relay the journey of a small group of soldiers returning to the rear after a lengthy stint on the front lines. They are exhausted and described as “old beggars under sacks.” This contrasts with the polished, orderly stereotype of the military that many in England held. This procession is no pompous military parade, it is a march of broken men “drunk with fatigue.”

Suddenly, chemical gas shells fall behind them, and an “ecstasy of fumbling” ensues as each soldier struggles to fit their gas-masks to their faces. Most are successful, but one is not. The speaker of the poem watches the poor man “guttering, choking, drowning” and dying through the fogged panes of his gas mask.

The final stanza is worth including in its entirety because it pointedly addresses an older generation of English citizens who sought to glorify the sacrifices of the conflict:

If in some smothering dreams, you too could paceBehind the wagon that we flung him in,And watch the white eyes writhing in his face,His hanging face, like a devil’s sick of sin;If you could hear, at every jolt, the bloodCome gargling from the froth-corrupted lungs,Obscene as cancer, bitter as the cudOf vile, incurable sores on innocent tongues, —My friend, you would not tell with such high zestTo children ardent for some desperate glory,The old Lie: Dulce et decorum estPro Patria mori.

Owen employs sensory imagery to great effect in the description of this soldier’s slow, agonizing death. It is interesting to note that Owen chooses to describe the death of a single soldier rather than a group or unit. This personalizes the experience of war for the reader and forces the war-supporters at home to face the individual horrors faced by the soldiers they sent to the front. This decision also avoided the common lionization of units who suffered mass casualties in battle as heroes, a tactic used by war-supporters that angered Owen.

For Owen, there is no glory in war: just mud, agony, blood and death. The poet believes that the worst offenders in the war were those safe in England parroting, the “old Lie” that it is honorable to die for your country. In Owen’s mind, the war was futile; his friends and comrades were dying for a falsehood. Through his poem “Dulce et Decorum Est,” Owen challenges his middle-aged English readers to acknowledge the sheer horror of the war their children were fighting.

The historical power of this poem is punctuated by the tragedy of the poet’s death. Owen was killed on the Western Front a mere week before the 1918 Armistice was signed. Owen’s mother received the telegram notifying her of her son’s death as church-bells rang to celebrate the ceasefire. Perhaps the fact that “Dulce et Decorum Est” is arguably the most famous poem to rise from the mud of the First World War shows that Wilfred Owen accomplished his goal of forcing people to confront the awful consequences of violence. I hope this helps!

War is presented as cruel and barbarous in this poem, set on a World War I battlefield. It opens not with soldiers depicted as young, strong and glorious, but describes them as old, sick, broken people:

Bent double, like old beggars ... coughing like hags.

It continues by noting how soldiers have lost their boots and limp on with bloody feet, "lame ... blind ... drunk with fatigue." There is nothing heroic in this depiction of the modern warrior. 

Owen then describes a mustard gas attack, particularly focusing on a soldier who gets caught in the attack without his gas mask on. Owen doesn't hold back in his graphic description of the man's fate: 

"white eyes writhing ... the blood come gargling from the froth-corrupted lungs/ obscene as cancer ... incurable sores ..."

Owen addresses the audience directly, telling them if they saw such sights they would not glorify war. He then calls the old phrase "dulce and decorum est," which means "it is sweet and fitting" to die for one's country, "the old Lie."

Owen wants his audience to see that war is horrible, not heroic, ghastly not glorious, and that it is not "sweet" to die for one's country.  

“Dulce Et Decorum Est” is a perfect example of poetry’s ability to reflect the changing worldview of an entire generation after World War I.  In fact, there was a popular saying in Britain after the war which one of my English professors often referred to during class:  “We went to war with Rupert Brooke, and came back with Siegfried Sassoon.  Like Sasson, Wilfred Owen’s poetry is filled with the shattered hopes and dreams of a nation after the first World War.   

Throughout “Dulce Et Decorum Est,” Owen uses several literary techniques to convey his anger and disillusionment brought on by the horror he witnessed on the battlefield.  The first, and most obvious, literary device is his use of imagery and metaphors.  The soldiers are compared to bent over beggars and hags stumbling through a nightmarish scene of “sludge…misty panes and thick green light.”  In contrast to the ironic title, Owens depicts the demise of soldiers not as ‘glorious’ but rather “obscene as cancer” and full of “writhing, gargling, and choking.”   

Owens also employs alliteration.  Some notable examples of this are found in lines 17 through 19 with the repetitive “s” sound and “w” sounds.

If in some smothering dreams you too could pace

Behind the wagon that we flung him in,

And watch the white eyes writhing in his face,  

Most importantly, however, is Owen’s use of biting sarcasm which accentuates his verbal irony found in the title and final two lines of the poem.  Translated, “Dulce et decorum est pro patria mori,” means “how sweet and right it is to die for your country.” The reader cannot miss his anger and bitterness directed towards those who have promised glory to “ardent children” but delivered nothing but death and heartache.  While many soldiers died, those who survived were left with disfigured bodies, disillusioned dreams, distrust of their nation, and a never-ending nightmare.

I assume that you are referring to "Dulce et Decorum Est" by Wilfred Owen, his most famous poem, and I have edited the question accordingly. Please remember in future to provide the title of the work you are referring to.

From the very opening words of this poem it is clear that Owen is playing with the image that his audience had of war and the actual brute reality of what fighting in WWI was like. Consider the first two lines of this incredible poem:

Bent double, like old beggars under sacks,

Knock-kneed, coughing like hags, we cursed through sludge...

War is shown to have transformed these young men into "beggars" and "hags" as they "curse" their way through the sludge of the battlefield. There are no romantic images here of war that indicate that it is something noble. Again and again in the first stanza images are supplied that show war as something that is dehumanising and something that strips away, rather than bestows, dignity, on the soldiers who are unfortunate to be caught in its path. Consider expressions such as "Men marched asleep," "blood-shod," "All went lame; all blind," "Drunk with fatigue." Clearly the man are beyond physical exhaustion and are shown to be walking like zombies, desperate to reach their rest.

Owen of course doesn't stop there in evoking the horrors of war. By presenting us with a disturbingly graphic image of one solder dying because of a gas attack, focusing on his "froth-corrupted lungs" and the "white eyes writhing in his face." Juxtaposing this event with what Owen calls "the old lie" he issues his challenge: it is not sweet and noble to die for one's country, and those who spread this lie to "children ardent for some desperate glory" are incredibly wrong.