How does Wilfred Owen give voice to experiences of WW1?

The First World War was a conflict in which the scale of the carnage and the general level of suffering were shocking to an unprecedented degree. All wars are shocking in some way, since men who have not been in combat before cannot have any real notion of what to expect, or of how bad it will be. World War I was even worse, partly because of technological changes, including the introduction of poison gas which Owen describes in his poetry, that supposedly were introduced to shorten the war but ended up intensifying the suffering of men in the field. The kind of warfare in which soldiers had to spend weeks or months in trenches—which had become necessary as protection from the improved accuracy and greater firepower of the guns—drove many of the men into a state of virtual madness, as the war dragged on year after year and no actual progress was made on the front.
Owen's verse puts this savagery into context. The British soldiers—like the Americans who entered the war later—had been told they were fighting for a noble cause, for democracy and to protect their way of life. George Orwell in his novel Coming up for Air describes a scene in which men begin cheering when the start of war is announced in 1914. All of this enthusiasm came to a crashing end once men saw the battlefield and its horrors. Men felt they had been duped by their leaders. This is what Owen means when he says,
If you could hear, at every jolt, the blood
Come gargling from the froth-corrupted lungs,
.....My friend, you would not tell with such high zest,
To children ardent for some desperate glory,
The old lie: dulce et decorum est pro patria mori.
The whole idea of its being "sweet and fitting to die for one's country" is revealed as a sham.
It was not only soldiers on the Allied side but those of the Central Powers as well who had this sense of having been tricked into serving for a supposedly glorious cause, only to see how worthless and destructive it was. The novel All Quiet on the Western Front shows the similar enthusiasm of German soldiers at the beginning, followed by the brutality and pointless suffering brought about by actual war. Owen's poetry encapsulates anti-war feeling in concentrated verse that shows the graphic effects of battle: gas poisoning, amputation in "Disabled", and shell-shock, which we now know as PTSD (Post-traumatic Stress Disorder), in "Mental Cases." His poetry set the tone for much of the anti-war literature, both poetry and prose, of the later twentieth century, including anti-Vietnam books such as Ron Kovic's Born on the Fourth of July.