How is the theme of loss explored in Wilfred Owen's poem Disabled?

Wildren Owen served in the British Army during one of the most horrific conflicts in human history, World War I. Trench warfare, chemical weapons, the introduction of new mechanized means of mass slaughter like the machine gun, and the disease and frostbite associated with protracted warfare in frigid conditions all characterized the war. Few who survived lived out their days unscarred emotionally from the experience. One would go on to lead Nazi Germany into the next and even more destructive world war, memories of the earlier conflict and its outcome shaping his views of Europe's future.

Owen was but one of millions who fought in World War I. He was, however, already taken with literature and poetry, and the influences of his war experiences are certainly felt in such works as his poem "Disabled." As students of the early period of the war know, each country, including late-entrant the United States, entered the conflict with idealistic and optimistic notions of warfare and heroism. "Disabled" is a reflection of the effects of warfare under the most inhumane of conditions on those previously enthusiastic young soldiers sent to fight wars started, to paraphrase another veteran of a later (Vietnam) war, Philip Caputo, by old men.

"Disabled" is about one of those young, vibrant kids sent off to war who returns crippled, physically and mentally, by his experiences. The sense of loss is for a life that no longer exists. Owen begins his poem focused not on that vibrant young man, but on the emotionally and physically crippled veteran he became:

He sat in a wheeled chair, waiting for dark,

And shivered in his ghastly suit of grey,

Legless, sewn short at elbow. Through the park

Voices of boys rang saddening like a hymn,

Voices of play and pleasure after day,

Till gathering sleep had mothered them from him.

This is obviously a melancholy opening to a poem, but Owen's point is clear: Here sits a human being from whom a life of joy has been taken. We don't yet know why, unless we know the author's background (which we do), but something horrible has befallen him. In the following stanzas, we are introduced to the once-youthful, athletic boy who relishes the physicality of sports and the testosterone-fueled pursuit of girls, specifically "Meg." Throughout these stanzas, however, we are repeatedly reminded of the toll war takes. The pretty girls he once pursued, and who were attracted to him, now keep their distance:

In the old times, before he threw away his knees, 

Now he will never feel again how slim

Girls' waists are, or how warm their subtle hands,

All of them touch him like some queer disease.

Not only is Owen's central figure physically disabled and disfigured from his wounds, but he now also suffers the emotional isolation of one cast aside by a society that no longer requires his services. As "Disabled" ends, the figure is socially as well as physically isolated, visited only by "a solemn man" who brings him fruit and thanks him for his service. To reemphasize the point of his poem, Owen writes in the final stanza, "Tonight he noticed how the women's eyes/ Passed from him to the strong men that were whole." 

The sense of loss that permeates "Disabled" is the loss of a future, once promising, now reduced to loneliness and pain, both physical and mental.