—Didn't appear to know a war was on,
Or see the blasted trench at which he stared.
"I'll do 'em in," he whined, "If this hand's spared,
I'll murder them, I will."
A low voice said,
"It's Blighty, p'raps, he sees; his pluck's all gone,
Dreaming of all the valiant, that AREN'T dead:
Bold uncles, smiling ministerially;
Maybe his brave young wife, getting her fun
In some new home, improved materially.
It's not these stiffs have crazed him; nor the Hun."
We sent him down at last, out of the way.
Unwounded;—stout lad, too, before that strafe.
Malingering?  Stretcher-bearers winked, "Not half!"
Next day I heard the Doc.'s well-whiskied laugh:
"That scum you sent last night soon died.  Hooray!"
The belief that he is unwounded is a wry comment; physically he was untouched, but emotionally and psychologically he was clearly deeply damaged. The dash creates another caesura, in which the irony is emphasised, even more so because he was a ‘stout lad’ — possibly with the physical potential to become an effective soldier. 
 A ‘strafe’ is an artillery attack which clearly terrified him.