How does the author of "Disabled" create sympathy for the ex-soldier?

Owens uses both imagery and contrast to build sympathy for the disabled soldier who lost his legs in World War I.
The poem opens with a description of the former soldier: he sits in a wheelchair in a

ghastly suit of grey, Legless, sewn short[.]

His plight is first contrasted to the pleasures of the happy children playing outside. Second, he remembers going out dancing with girls in the "old days," before he "threw away his knees." Now young women look at him with pity and "touch him like some queer disease."
Third, he remembers how he liked to play football (soccer) when he was younger, and how after a game, he felt he had to enlist in the army to impress his girlfriend, Meg. Next, he remembers how glorious he thought war would be:

He thought of jewelled hilts For daggers in plaid socks; of smart salutes

Ironically, instead of making him a hero, war has left him to be pitied, dependent on others:

Now, he will spend a few sick years in institutes, And do what things the rules consider wise, And take whatever pity they may dole.

Ironically, too, although he joined the war to impress a girl, the war has left him as someone the girls' eyes pass over to "the strong men that were whole."
Through imagery and through the contrast of his bleak life as a disabled war veteran with his happier past, we grow to feel sympathetic to this young soldier, who was sold on a false idea of what warfare is like.